TORONTO - Ontario would need to see scientific proof that hydraulic fracturing, or fracking, is safe before it allows energy companies to use the controversial practice to extract natural gas, Premier Dalton McGuinty said Tuesday.

No private companies have approached the province to request permission to frack, which involves the use of chemically-treated water under extreme pressure in drill holes to fracture underground shale and release gas or oil.

"If somebody was to approach us and say would you consider fracking in Ontario, I think the first thing we’d have to say is: 'Hang on a second now. We’re going to have to take a look at the latest evidence associated with fracking, the risks. There have been some experts who’ve written about the risks associated with water,'" said McGuinty.

"I think we’d have to take a long hard look at the scientific evidence before we’d give a thumbs-up or a thumbs-down, but at this point in time, it’s purely academic."

The New Democrats shared McGuinty's concerns about negative environmental impacts from fracking, especially on drinking water.

"We’ve been watching what’s been happening across the country and across North America on the fracking issue, and one of the things we’re obviously concerned about is making sure that water tables are safe, making sure that the process doesn’t threaten other important environmental considerations," said NDP Leader Andrea Horwath.

However, the Progressive Conservatives said they were "very optimistic" about the jobs that could be created if fracking were approved in Ontario.

"There’s 100 years of affordable energy that can come from it," said PC energy critic Vic Fedeli.

"We’re very encouraged by it and everything we’ve seen to this point, from all the engineers and experts, talks about the safety and the environmental safety of it."

Opponents of fracking said companies including Mooncor Oil and Gas and Dundee Energy are buying up land in southwestern Ontario, especially the Kettle Point area on Lake Huron, that could be used for fracking.

"Mooncor has not announced any plans to frack in Ontario," company spokesman Nick Tsimidis said in an email Tuesday. Dundee Energy did not immediately reply to requests for an interview.

The Council of Canadians opposes fracking, and wants Ontario to follow Quebec's lead and impose a moratorium on the practice. It warns fracking in Ontario could have serious long-term and cumulative impacts on the Great Lakes.

Quebec has a moratorium on fracking and all oil and gas exploration activities under the Saint Lawrence River, but other provinces, including British Columbia, Alberta and Saskatchewan, allow fracking.

At least 175,000 wells have been fracked in Canada, the majority of them in Alberta.

Nova Scotia had some fracking operations in 2007-08, but the NDP government has said it won't approve any more hydraulic fracturing until a review of the process is completed in 2014.

A report done for the New Brunswick government, released in October, said the province should proceed with shale gas exploration but with a phased-in approach that would limit it to one to three sites to allow for research and development.

The B.C. Oil and Gas Commission said in September that a spate of small earthquakes in the province's northeastern corner were caused by fracking in the Horn River Basin, a gas-rich shale formation that's attracted some of the industry's biggest players. The 38 quakes ranged between magnitudes of 2.2 and 3.8 on the Richter scale.

Last December, the U.S. Environmental Protection Agency, for the first time, implicated fracking in causing ground water pollution. The EPA announced it found compounds likely associated with fracking chemicals in the groundwater beneath a Wyoming community where residents say their well water reeked of chemicals.

The issue has caught the attention of some celebrities, with Yoko Ono, Paul McCartney, Lady Gaga and actor Alec Baldwin joining Artists Against Fracking in New York state.

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  • In this file photo from Oct. 14, 2011, a drilling rig is seen in Springville, Pa. State regulators blamed faulty gas wells drilled for leaking methane into the groundwater in nearby Dimock, Pa. It was the first serious case of methane migration said to be related to the Pennsylvania Marcellus Shale gas field drilling boom. (AP Photo/Alex Brandon, FILE)

  • British police secure the area where demonstrators erected a mock fracking rig with a banner reading 'No fracking in the UK' in a protest against hydraulic fracturing for shale gas outside the Houses of Parliament in London on December 1, 2012. AFP PHOTO / JUSTIN TALLIS

  • SPRINGVILLE, PA - JANUARY 18: A truck with the natural gas industry, one of thousands that pass through the area daily, drives through the countryside to a hydraulic fracturing site on January 18, 2012 in Springville, Pennsylvania. (Photo by Spencer Platt/Getty Images)

  • SAN FRANCISCO, CA - MAY 30: Protestors stage a demonstration against fracking in California outside of the Hiram W. Johnson State Office Building on May 30, 2013 in San Francisco, California. Dozens of protesters with the group Californians Against Fracking staged a protest outside of California Gov. Jerry Brown's San Francisco offices demanding that Gov. Brown ban fracking in the state. (Photo by Justin Sullivan/Getty Images)

  • People demonstrate on August 3, 2013 in La Petite Brosse, near Jouarre, outside Paris, to protest against an exploratory oil shale drilling, considering that it opens the door to the exploration of shale gas in the Parisian Basin. Banner reads 'Stop gas and oil shale'. AFP PHOTO / PIERRE ANDRIEU

  • In this Nov. 26, 2012 photo, Steve Lipsky demonstrates how his well water ignites when he puts a flame to the flowing well spigot outside his family's home in rural Parker County near Weatherford, Texas. The U.S. Environmental Protection Agency had evidence a gas company's drilling operation contaminated Lipsky's drinking water with explosive methane, and possibly cancer-causing chemicals, but withdrew its enforcement action, leaving the family with no useable water supply, according to a report obtained by The Associated Press. The EPA's decision to roll back its initial claim that hydraulic fracturing, or “fracking,” operations had contaminated the water is the latest case in which the federal agency initially linked drilling to water contamination and then softened its position, drawing criticism from Republicans and industry officials who insisted they proved the agency was inefficient and too quick to draw conclusions. (AP Photo/LM Otero)

  • In this file photo of Jan. 17, 2013, Yoko Ono, left, and her son Sean Lennon visit a fracking site in Franklin Forks, Pa., during a bus tour of natural-gas drilling sites in northeastern Pennsylvania. Ono and Lennon have formed a group called “Artists Against Fracking,” which has become the main celebrity driven anti-fracking organization. (AP Photo/Richard Drew, File)

  • In this March 29, 2013 file photo, a worker checks a dipstick to check water levels and temperatures in a series of tanks at a hydraulic fracturing operation at a gas drilling site outside Rifle, Colorado. (AP Photo/Brennan Linsley)

  • In this March 29, 2013 file photo, a worker switches well heads during a short pause in the water pumping phase, at the site of a natural gas hydraulic fracturing and extraction operation outside Rifle, in western Colorado. (AP Photo/Brennan Linsley)

  • In this March 29, 2013 file photo, workers tend to a well head during a hydraulic fracturing operation at a gas well outside Rifle, in western Colorado. (AP Photo/Brennan Linsley)

  • Josh Fox, director of the anti-fracking, Oscar-nominated documentary “Gasland” testifies during a House Committee hearing on oil drilling, "fracking" legislation at the Illinois State Capitol Tuesday, May 21, 2013, in Springfield, Ill. (AP Photo/Seth Perlman)

  • This is a Thursday Aug. 15, 2013 image of the Cuadrilla exploration drilling site in Balcombe, southeast England. (AP Photo/Gareth Fuller/PA)

  • A child plays near a farmers' protest in an area where oil company Chevron plans to put a drilling rig exploring for shale gas in the south-eastern Polish village of Zurawlow on June 11, 2013. AFP PHOTO / JANEK SKARZYNSKI

  • Protesters hold a banner during a protest outside of the Momentive resin plant, Monday, July 8, 2013, in Morganton, N.C. Dozens of environmental activists blocked a chemical plant Monday to protest against the company's sale of products used in the natural gas drilling process called hydraulic fracturing, or fracking. (AP Photo/The News Herald, Mary Elizabeth Robertson)

  • A fracking rig exploring for shale gas of oil company Chevron on June 11, 2013 in a village of Ksiezomierz in south-eastern Poland. AFP PHOTO / JANEK SKARZYNSKI

  • People demonstrate on August 3, 2013 in La Petite Brosse, near Jouarre, outside Paris, to protest against an exploratory oil shale drilling, considering that it opens the door to the exploration of shale gas in the Parisian Basin. AFP PHOTO / PIERRE ANDRIEU

  • Opponents of hydraulic fracturing in New York state attend a news conference and rally against hydraulic fracturing, also known as fracking, on January 11, 2012 in New York City. (Photo by Spencer Platt/Getty Images)

  • Eric Weltman of Food & Water Watch attends a news conference and rally against hydraulic fracturing, also known as fracking, in New York State on January 11, 2012 in New York City. (Photo by Spencer Platt/Getty Images)

  • Opponents and supporters of gas-drilling, or fracking, walk into the last of four public hearings on proposed fracking regulations in upstate New York on November 30, 2011 in New York City. (Photo by Spencer Platt/Getty Images)

  • Engineers on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers at work on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • General views of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers look at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • A lump of shale rock on display at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Engineers at work on the drilling platform of the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Drill heads on display at the entrance to the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • An engineer displays a lump of shale rock at the Cuadrilla shale fracking facility on October 7, 2012 in Preston, Lancashire. (Photo by Matthew Lloyd/Getty Images)

  • Actor/director Mark Ruffalo (C) speaks at the Hydraulic Fracturing prevention press conference urging the protection of the drinking water source of 15 million Americans at Foley Square on April 25, 2011 in New York City. (Photo by D Dipasupil/Getty Images)

  • (L-R) Actor/director Mark Ruffalo, Denise Katzman, Wenonah Hauter, and Water Defense co-founder/campaign director Claire Sandberg attend the Hydraulic Fracturing prevention press conference urging the protection of the drinking water source of 15 million Americans at Foley Square on April 25, 2011 in New York City. (Photo by D Dipasupil/Getty Images)