Fracking triggered a 4.4-magnitude earthquake in northeastern B.C. last year, CBC News has learned, making it one of world's largest earthquakes ever triggered by the controversial process.

B.C.'s Oil and Gas Commission confirmed the cause of the earthquake in an email statement to CBC this week, saying it was "triggered by fluid injection during hydraulic fracturing."

The 4.4-magnitude quake was felt in Fort St. John and Fort Nelson in August 2014. It was preceded by a 3.8-magnitude earthquake in late July, also caused by fracking.

B.C.'s Oil and Gas Commission told CBC that several companies were doing hydraulic fracturing in the area at the time, and several more were disposing of fracking waste.

But the commission says it was Progress Energy's operations that were "associated with triggering this event."

Hydraulic fracturing, often called fracking, is the process of injecting water, sand and chemicals at high pressure deep underground to break rock and free gas.

Fracking fluid reduced

Since the 2014 earthquake, Progress Energy has been ordered to reduce the volume of fracking fluid being used, and the company has complied, according to the commission.

As well, new seismic equipment has been set up in the area. No new earthquakes have been detected in the immediate area.

Last week, Progress Energy temporarily shut down another fracking site after a 4.6-magnitude earthquake hit just three kilometres away. 

Responding to The Canadian Press late Wednesday, Progress Energy said the cause of the recent quake has not yet been established.

"The northeast B.C. foothills is a seismically active area with more than 6,000 seismic events each year, 99 per cent of which measure a magnitude so low that they are not felt on the surface," said a statement from spokesperson Dave Sterna.

The company has voluntarily installed 17 seismic monitoring stations in its operating area, Sterna added.

Officials say it will take several more weeks to determine if the 4.6-magnitude quake was triggered by fracking.

Sign of things to come?

Progress Energy is owned by Petronas of Malaysia, which also owns Pacific NorthWest LNG, the firm planning to build a giant liquefied natural gas export facility near Prince Rupert, B.C. supplied by gas fracked in northeastern B.C.

Matt Horne, with clean energy advocate the Pembina Institute, calls the significant earthquake "another warning sign for what could be down the road.

"If B.C. goes down the LNG road in a big way, it's really important when we're debating LNG proposals, we're eyes wide open.... to both the benefits and impacts. Increased earthquakes is one of those impacts," said Horne.

B.C.'s Oil and Gas Commission declined a taped interview, providing only background information by email.

Minister says events are 'rare'

In a statement, B.C. Minister of Natural Gas Development Rich Coleman said "felt seismic events related to hydraulic fracturing are rare."

"The province has a leading role in North America in the detection and mitigation of induced seismicity associated with unconventional gas development and works closely with the Oil and Gas Commission and industry," the statement said.

The statement went on to emphasize that drilling must stop immediately if "seismicity reaching a magnitude of 4.0 is detected."

"Operations can only resume once a mitigation plan – such as reduced pumping pressures – are agreed on by the Commission," it said.

Peace MLAs Mike Bernier and Pat Pimm didn't respond to requests for comment. 

In January, Alberta's energy regulator reported fracking likely caused a 4.4-magnitude earthquake in the northern town of Fox Creek. Scientists told CBC at the time the quake was the largest in the world ever caused by fracking.