Two Canadians who have been detained in an Egyptian prison for over a month will be going on a hunger strike.

Tarek Loubani of London, Ont., and John Greyson of Toronto were arrested in Cairo on Aug. 16. They have yet to face formal charges.

Greyson's sister, Cecilia, and a friend of the Canadians, Justin Podur, released a statement on Monday that said the men had informed friends and supporters through their Egyptian lawyers of the decision to go on a hunger strike.

"They will be refusing food beginning September the 16th to protest the arbitrary nature of their detention by Egyptian authorities," the release said.

On Sunday, Podur told CBC News that Greyson and Loubani's "detention has been extended … for 15 days."

Loubani, a doctor, and Greyson, a filmmaker and university professor, had been intending to make their way to Gaza last month when they were arrested.

“We can only imagine the anguish that John and Tarek feel after realizing that their detention could be extended for so long in what can only be described as an arbitrary process that lacks any credibility,” Cecilia said on Monday.

Monday's release said it's believed the Canadians' detention could be extended up to two years without any charges being laid.

“We know that they did not take the decision to begin a hunger strike lightly, and we want them to know we will do everything we can to support them and get them home soon," Cecilia said.

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  • Jan. 25 - Feb. 11, 2011

    Egyptians stage nationwide demonstrations against nearly 30 years of President Hosni Mubarak's rule. Hundreds of protesters are killed as Mubarak and his allies try to crush the uprising. <em>Anti-government protestors continue to defy the curfew in Tahrir Square on February 1, 2011 in Cairo, Egypt. (Photo by Peter Macdiarmid/Getty Images)</em>

  • Feb. 11

    Mubarak steps down and the military takes over. The army dissolves parliament and suspends the constitution, meeting two key demands of protesters. <em>In this Friday, Feb. 11, 2011 file photo taken from Egyptian television, Egypt's vice president Omar Suleiman makes the announcement that Egyptian President Hosni Mubarak has stepped down from office, in Cairo, Egypt. (AP Photo/Egypt TV, File)</em>

  • Nov. 28, 2011 - Feb 15, 2012

    Egypt holds multistage parliamentary elections. In the lawmaking lower house, the Muslim Brotherhood wins nearly half the seats, and ultraconservative Salafis take another quarter. The remainder goes to liberal, independent and secular politicians. In the largely powerless upper house, Islamists take nearly 90 percent of the seats. <em>A woman places her vote in the ballot box at a polling station in the Shubra district on the second day of voting on November 29, 2011 in Cairo, Egypt. (Photo by Peter Macdiarmid/Getty Images)</em>

  • May 23 - 24, 2012

    The first round of voting in presidential elections has a field of 13 candidates. The Brotherhood's Mohammed Morsi and Ahmed Shafiq, the last prime minister under Mubarak, emerge as the top two finishers, to face each other in a runoff. <em>Polling center officials sort ballots for counting following the second day of Egypt's presidential election on May 24, 2012 in Cairo, Egypt. (Photo by John Moore/Getty Images)</em>

  • June 14

    The Supreme Constitutional Court orders the dissolving of the lower house of parliament. <em>A security officer stands outside the Supreme Constitutional Court in Cairo, on February 3, 2013 as Egypt's top court postponed until March 3, a ruling on the legality of the Islamist-dominated commission that drafted a contested new constitution, state media reported. (KHALED DESOUKI/AFP/Getty Images)</em>

  • June 16 - 17

    Egyptians vote in the presidential runoff between Morsi and Shafiq. Morsi wins with 51.7 percent of the vote. <em>Egyptian women check for their names on an electoral list at a polling station on June 17, 2012 in Cairo, Egypt. (Photo by Daniel Berehulak /Getty Images)</em>

  • June 30

    Morsi takes his oath of office. <em>In this image released by the Egyptian Presidency, Egyptian President Mohammed Morsi, center, stands with judges Farouk Sultan, left, and Maher el-Beheiri, right, as he is sworn in at the Supreme Constitutional Court in Cairo, Egypt, Saturday, June 30, 2012. (AP Photo/Ahmed Fouad, Egyptian Presidency)</em>

  • Nov. 19

    Members of liberal parties and representatives of Egypt's churches withdraw from the 100-member assembly writing the constitution, protesting attempts by Islamists to impose their will. <em>A Coptic Christian monk holds a Coptic cross at Al-Mahraq monastery during the preparation of a religious festival in Assiut, Upper Egypt, Tuesday, Aug. 6, 2013. (AP Photo/Manu Brabo)</em>

  • Nov. 22

    Morsi unilaterally decrees greater powers for himself, giving his decisions immunity from judicial review and barring the courts from dissolving the constituent assembly and the upper house of parliament. The move sparks days of protests. <em>Thousands of Egyptian President Mohammed Morsi supporters gather outside the presidential palace in Cairo on November 23, 2012. (AHMED MAHMOUD/AFP/Getty Images)</em>

  • Nov. 30

    Islamists in the constituent assembly rush to complete the draft of the constitution. Morsi sets a Dec. 15 date for a referendum. <em>A view of Cairo's Tahrir Square taken on November 29, 2012 shows tents set up by protesters on the third day of protest over Egyptian President Morsi's decision to grant himself sweeping powers until the new constitution is ratified in a referendum. (MAHMOUD kHALED/AFP/Getty Images)</em>

  • Dec. 4

    More than 100,000 protesters march on the presidential palace, demanding the cancellation of the referendum and the writing of a new constitution. The next day, Islamists attack an anti-Morsi sit-in, sparking street battles that leave at least 10 dead. <em>Egyptian protesters chant anti-Muslim Brotherhood slogans during a rally in front of the presidential palace, in Cairo, Egypt, Tuesday, Dec. 4, 2012. (AP Photo/Nasser Nasser)</em>

  • Dec. 15, Dec. 22

    In the two-round referendum, Egyptians approve the constitution, with 63.8 percent voting in favor. Turnout is low. <em>A man dips his finger on an ink pad to mark his having voted during a referendum on the new Egyptian constitution at a polling station on December 15, 2012 in Cairo, Egypt. (Photo by Daniel Berehulak/Getty Images)</em>

  • Jan. 25, 2013

    Hundreds of thousands hold protests against Morsi on the 2-year anniversary of the start of the revolt against Mubarak, and clashes erupt in many places. <em>An Egyptian protester wearing empty tear gas canisters around his neck carries an Egyptian flag during a demonstration in Tahrir Square on January 25, in Cairo, Egypt. (Photo by Ed Giles/Getty Images).</em>

  • Feb. - March 2013

    Protests rage in Port Said and other cities for weeks, with dozens more dying in clashes. <em>Egyptian mourners carry body of Abdelhalim Mehana who was killed during clashes with riot police on March 4, during his funeral procession in the Suez Canal city of Port Said on March 8, 2013, a day before a court is to issue verdicts over the killing of people in a football riot there. (KHALED DESOUKI/AFP/Getty Images)</em>

  • April 7

    A Muslim mob attacks the main cathedral of the Coptic Orthodox Church as Christians hold a funeral and protest there over four Christians killed in sectarian violence the day before. Pope Tawadros II publicly blames Morsi for failing to protect the building. <em>Unidentified Egyptians throw stones towards Coptic Christians during sectarian clashes outside the Egyptian Coptic cathedral in Cairo's Abbassiya neighbourhood on April 7, 2013. (AFP/Getty Images)</em>

  • June 23

    A mob beats to death four Egyptian Shiites in a village on the outskirts of Cairo. <em>Egyptians carry the coffin of a Shiite following funeral prayers in Cairo, Egypt, Monday, June 24, 2013. (AP Photo/Amr Nabil)</em>

  • June 30

    Millions of Egyptians demonstrate on Morsi's first anniversary in office, calling on him to step down. Eight people are killed in clashes outside the Muslim Brotherhood's Cairo headquarters. <em>Egyptian opposition protesters chant during a demonstration in Tahrir Square as part of the 'Tamarod' campaign on June 30, 2013 in Cairo, Egypt. (Photo by Ed Giles/Getty Images).</em>

  • July 1

    Huge demonstrations continue, and Egypt's powerful military gives the president and the opposition 48 hours to resolve their disputes, or it will impose its own solution. <em>Fireworks light the sky as hundreds of thousands of Egyptian demonstrators gather outside the presidential palace in Cairo during a protest calling for the ouster of President Mohamed Morsi on June 30, 2013. (KHALED DESOUKI/AFP/Getty Images)</em>

  • July 2

    Military officials disclose main details of the army's plan if no agreement is reached: replacing Morsi with an interim administration, canceling the Islamist-based constitution and calling elections in a year. Morsi delivers a late-night speech in which he pledges to defend his legitimacy and vows not to step down. <em>Egyptian opposition protesters demonstrate at the Egyptian Presidential Palace in the suburb of Heliopolis on July 2, 2013 in Cairo, Egypt. (Photo by Ed Giles/Getty Images)</em>

  • July 3

    Egypt's military chief announces that Morsi has been deposed, to be replaced by the Chief Justice of the Supreme Constitutional Court until new presidential elections. No time frame is given. Muslim Brotherhood leaders are arrested. Tens of thousands of Morsi supporters remain camped out in two mass sit-ins in Cairo's streets. <em>Egyptian Army soldiers patrol the streets outside Cairo University after a broadcast confirming that the army will temporarily be taking over from the country's first democratically elected president Mohamed Morsi on July 3, 2013 in Cairo. (MAHMOUD KHALED/AFP/Getty Images)</em>

  • July 4

    Supreme Constitutional Court Chief Justice Adly Mansour is sworn in as Egypt's interim president. <em>Egypt's chief justice Adly Mansour prepares to swear in as the nation's interim president Thursday, July 4, 2013. (AP Photo/Amr Nabil)</em>

  • July 5

    Mansour dissolves the Islamist-dominated upper house of parliament as Morsi's supporters stage mass protests demanding his return. Clashes between pro- and anti-Morsi groups in Cairo and Alexandria, and violence elsewhere leave at least 36 dead. A Brotherhood strongman, deputy head Khairat el-Shater, is arrested. <em>An anti-Mohammed Morsi protester is attended to after allegedly being shot by Muslim Brotherhood supporters in Tahrir Square during fighting between the two camps on July 5, 2013 in Cairo, Egypt. (Photo by Spencer Platt/Getty Images)</em>

  • July 8

    Egyptian soldiers open fire on pro-Morsi demonstrators in front of a military base in Cairo, killing more than 50. Each side blames the other for starting the clash near the larger of the two sit-ins, near east Cairo's Rabaah al-Adawiya mosque. Mansour puts forward a time line for amending the constitution and electing a new president and parliament by mid-February. The Brotherhood refuses to participate in the process. <em>A man reacts after seeing the body of a family member at the Liltaqmeen al-Sahy Hospital in Cairo's Nasr City district, allegedly killed during a shooting at the site of a pro-Morsi sit-in in front of the headquarters of the Egyptian Republican Guard on July 8, 2013 in Cairo, Egypt. (Photo by Ed Giles/Getty Images)</em>

  • July 9

    Mansour appoints economist Hazem el-Beblawi as prime minister and opposition leader Mohamed ElBaradei as vice president. A military announcement backs up the appointments. <em>In this Tuesday, July 9, 2013 file photo released by the Egyptian Presidency, Hazem el-Beblawi meets with interim President Adly Mansour, unseen, in Cairo, Egypt. (AP Photo/Egyptian Presidency, File)</em>

  • July 26

    Millions pour into the streets of Egypt after a call by the country's military chief for protesters to give him a mandate to stop "potential terrorism" by supporters of Morsi. Five people are killed in clashes. Prosecutors announce Morsi is under investigation for a host of allegations including murder and conspiracy with the Palestinian militant group Hamas. <em>Supporters of the Egyptian Army take part in a demonstration at Tahrir Square on July 26, 2013 in Cairo, Egypt. (Photo by Ed Giles/Getty Images).</em>

  • July 27

    Security forces and armed men in civilian clothes clash with Morsi supporters outside the larger of the two major sit-ins in Cairo, killing at least 80 people. <em>A supporter of deposed Egyptian President Mohammed Morsi prays prior to the 'iftar' fast-breaking meal at a sit-in protest at the Rabaa al Adweya Mosque in the Nasr City district on July 28, 2013 in Cairo, Egypt. (Photo by Ed Giles/Getty Images).</em>

  • July 30

    The EU's top diplomat Catherine Ashton holds a two-hour meeting with detained Morsi at an undisclosed location. She is one of a number of international envoys, including U.S. Sens. John McCain and Lindsey Graham, to visit Egypt to attempt to resolve the crisis. <em>This image released by the Egyptian Presidency shows interim Vice President Mohamed El Baradei, right, making remarks at a joint news conference with EU foreign policy chief Catherine Ashton, left, at the presidential palace in Cairo, Egypt, Tuesday, July 30, 2013. (AP Photo/Egyptian Presidency)</em>

  • Aug 7

    Egypt's presidency says that diplomatic efforts to peacefully resolve the standoff between the country's military-backed interim leadership and the Muslim Brotherhood have failed. <em>Supporters of Egypt's ousted President Mohammed Morsi attend the Eid al-Fitr dawn prayers, marking the end of the Muslim holy fasting month of Ramadan outside Rabaah al-Adawiya mosque, where protesters have installed a camp and hold daily rallies at Nasr City in Cairo, Egypt, Wednesday, Aug. 8, 2013. (AP Photo/Khalil Hamra)</em>

  • Aug 11

    Egyptian security forces announce that they will besiege the two sit-ins within 24 hours to bar people from entering. <em>Supporters of deposed Egyptian president Mohamed Morsi (portrait) cheer during a football match between the two main Cairo protest camps by members of the Muslim Brotherhood and backers of the ousted Islamist leader set up at the Nahda and Rabaa al-Adawiya squares, on August 11, 2013 in Cairo's al-Nahda square. (KHALED DESOUKI/AFP/Getty Images)</em>

  • Aug 12

    Authorities postpone plans to take action against the camps, saying they want to avoid bloodshed after Morsi supporters reinforce the sit-ins with thousands more protesters. <em>Members of the Muslim Brotherhood and supporters of Egypt's ousted president Mohammed Morsi (portrait) demonstrate outside the High Court in Cairo on August 12, 2013. (GIANLUIGI GUERCIA/AFP/Getty Images)</em>