Police would say only that the search warrant had been executed, and would not confirm media reports that the raid took place at a Mississauga storage facility where old government computers are kept.
Police were called in after the Progressive Conservatives complained senior staff in McGuinty's office deleted emails about the Liberal's decision to kill planned gas plants in Oakville and Mississauga prior to the 2011 election, at a cost of up to $1.1 billion.
The Tories complained the Liberals repeatedly refused to produce all documents on the gas plant cancellations that had been requested by a legislative committee, and even Ontario's Privacy Commissioner complained she had been misled about deleted government email accounts.
Premier Kathleen Wynne's office says she broadened the scope of the committee hearings and produced more documents since taking over from McGuinty, and "will continue to co-operate fully in any effort to gather information."
The gas plant hearings, which have been going on for more than a year, resumed Tuesday when the legislature returned from the 10-week Christmas break.