OTTAWA: Fracking by a Canadian subsidiary of Malaysian oil and gas giant Petronas triggered one of the world’s largest earthquakes linked to the controversial practice, Canadian media said Wednesday. The British Columbia Oil and Gas Commission said it has linked the operations of Progress Energy in the province’s northeast to a 4.4-magnitude quake felt in Fort St John in August 2014, the CBC reported. It was preceded by a 3.9-magnitude quake in July the same year, also believed to have been caused by fracking. Fracking or hydraulic fracturing is a process used to extract shale gas by blasting a high-pressure mixture of water, sand and chemicals deep underground to release hydrocarbons trapped between layers of rock. Environmentalists argue that the process may contaminate ground water and even cause small earthquakes.