A timeline of key events in Ontario's gas plants cancellation scandal:

September 2009: Ontario Power Authority accepts TransCanada’s bid to build a 900-megawatt natural gas-fired power generation plant in Oakville.

Oct. 1, 2010: At a fundraiser for Citizens for Clean Air Oakville, high-profile environmental activist Erin Brockovich speaks against the proposed gas-fired plant.

Oct. 7, 2010: Ontario government announces the cancellation of the Oakville power plant

Sept. 28, 2011: During the provincial election campaign, Liberal candidate Charles Sousa announces plan to cancel a gas plant in the midst of construction in Mississauga. Construction continues for another two months.

Oct. 6, 2011: On election day, Liberals under Premier Dalton McGuinty hold on to all their seats in Mississauga-Oakville area.

July 16, 2012: Liberals announce the decision to halt construction on Mississauga plant and relocate it to Sarnia will cost $190 million.

Sept. 24, 2012: Chris Bentley, then the energy minister, announces deal with TransCanada to relocate proposed Oakville plant to Bath, Ont. Claims total cost of cancelling the plant is $40 million. That same day, Liberals release 36,000 documents on the two cancelled gas plants. McGuinty and Bentley claim that’s all the documents that exist.

Oct. 2, 2012: Opposition parties send Progressive-Conservative-introduced contempt motion against Bentley to legislative committee for public hearings.

Oct. 15, 2012: Days after 20,000 more pages of gas plants documents are released, McGuinty announces he’s resigning as premier and prorogues legislature.

Feb. 28, 2013: Newly elected Liberal leader and Premier-designate Kathleen Wynne expands mandate of justice committee investigation into cancelled gas plants.

Mar. 8, 2013: Justice Committee hearings resume into cancelled plants and contempt motion, revived by PCs.

June 7, 2013: Ontario Provincial Police launch criminal investigation into the destruction of emails related to the cancellation of the gas plants by Liberal staffers.

Oct. 8, 2013: Auditor General Bonnie Lysyk pegs cost of cancelling the Oakville gas plant at between $675 million and $815 million. Estimated total costs of cancelling both plants reaches the $1-billion mark.

Mar. 27, 2014: OPP allege David Livingston, McGuinty’s last chief of staff, hired a staffer’s boyfriend to wipe clean government hard drives that contained information about the gas plant scandal. Police say the hard drives will “afford evidence” of breach of trust.

With files from The Canadian Press