Aaron Yoon, who is about 24, has been in a prison in Nouakchott, the capital of Mauritania, since at least the summer of 2012, CBC News has learned. He appears to have had no role in the Algerian gas plant attack in January of this year.
Before his arrest, Yoon attended a religious school in Mauritania, reportedly with Americans and Europeans, studying the Qur'an.
But something happened to make authorities suspicious and Yoon, known by his Muslim name Haroon Yoon, was arrested.
On Thursday, the RCMP confirmed that the remains of Ali Medlej and Xris Katsiroubas, who were also from London, Ont. and went to high school with Yoon, were found at the site of the deadly attack on an Algerian gas plant.
CBC News had previously revealed the identities of the two, who are believed to have travelled to the North African country to join al-Qaeda and international militants who staged the deadly attack on the gas plant there in January.
Yoon, was raised a Catholic, but he converted to Islam a year before graduating high school.
Embassy official met with Yoon
Mauritania's ambassador to Canada, Ahmed Ould Teguedi, told CBC's Melissa Kent that a representative from Canada's embassy in Rabat, Morocco traveled to Mauritania and met with Yoon in detention as well as government officials from the Ministry of the Interior and the Justice Ministry.
He said Yoon's conditions in detention are good, that he will be judged in a 'transparent' manner and that he may even have one or more Canadian lawyers defending him
A human rights activist in Mauritania told CBC News he was jailed the same time as Yoon and saw him behind bars.
The activist said Yoon was part of a group accused of having a relationship with al-Qaeda.
In July 2012, the activist, then out of jail, wrote about Yoon. Other prisoners had contacted him with borrowed phones to say Yoon had a urinary tract infection and had briefly lost consciousness.
Yoon is reportedly fine now and continues to profess his innocence.
RCMP asks for public's help
Meanwhile, during a Thursday news conference, RCMP Supt. Marc Richer said the police force is "seeking the assistance of the public" to find out more about the events leading up to Medlej and Katsiroubas going overseas.
The RCMP is saying little about their investigation. Richer said it has been underway for "a number of months."
Asked whether the RCMP are still trying to determine if the remains of other Canadians are at the Algerian gas plant, Richer replied: "I will tell you that the work with respect to the remains continues."
How Medlej and Katsiroubas became involved in the gas plant attack isn't yet clear, but sources suggest they were influenced by one man operating in southwestern Ontario.
CBC News has learned that RCMP in London were asking questions about the three men in June 2012, seven months before the Algeria attack.