A police investigation into the Ontario government's billion-dollar cancellation of two gas-fired power plants has ratcheted up, with officers executing a search warrant, reportedly at a data storage company.

The development in the case -- which involves accusations former premier Dalton McGuinty's staff destroyed government documents to cover up the scandal -- signals that the Ontario Provincial Police have amassed enough evidence to convince a judge to let them step up their probe.

"There was a search warrant," OPP Sgt. Carolle Dionne said. "The investigation is still ongoing."

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Sgt. Dionne would not reveal the location of the search, but the Ottawa Citizen reported it as the local facilities of international data storage company Recall, on Timberlea Blvd. in Mississauga.

Employees at Recall could not be reached for comment.

The search is at least the second the OPP have undertaken: police visited the premier's office last November. On Wednesday, Premier Kathleen Wynne's staff refused to say if investigators used a search warrant. A source close to government described that visit as "casual."

The investigation started last year after a legislative committee discovered that some of Mr. McGuinty's staffers regularly deleted all of their emails, potentially destroying valuable evidence related to the gas plants.

An investigation by information and privacy commissioner Ann Cavoukian further revealed that David Livingston, Mr. McGuinty's chief of staff, asked the head of the province's civil service for advice on wiping computer hard drives.

The OPP met with Ms. Cavoukian and her team last summer and asked specific questions about her office's investigation, said Trell Huether, a spokesman for the Privacy Commissioner. "We provided our full cooperation, including notes," he said Wednesday.

The opposition parties claim the e-mail deletions were an attempt to cover up the political gamesmanship behind the plant cancellations.

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"There have always been two parts to this scandal. The first was: how much did it cost the taxpayer? The second was: who ordered the cover-up?" PC MPP Vic Fedeli said Wednesday.

NDP House Leader Gilles Bisson said he hoped the investigation would shed light on whether any of the deleted emails or other documents had been preserved on a server.

"We're going to need to know what was found and who was involved?" he said. "Where did all these emails go to?"

The government faces a contempt of parliament charge over opposition accusations they witheld information on the plants. The Liberals insisted Wednesday that Ms. Wynne had cooperated with legislators, pointing to the thousands of pages of non-deleted emails and other records released to the committee.

"Since day one, the Premier has been open and transparent about the Mississauga and Oakville gas plant relocations," spokeswoman Zita Astravas wrote in an email.

The Liberals pulled the plug on the plants, in the Toronto suburbs of Mississauga and Oakville in what was widely seen as a ploy to win area seats in the 2011 election. An audit pegged the cost of the decision at up to $1-billion.