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Ah, the beautiful wilds of western Canada. Rivers, mountains, forests… and out-of-control oil leaks that have already spurted thousands of barrels of toxic bitumen into the environment.

The leaks were caused by an underground blowout at a tar sand project in north-east Alberta run by Canadian Natural Resources that had been certified safe by government regulators. One of the firm’s scientists has been reported saying that they are . The company hasn’t disclosed how fast the leaks are progressing.

Since May, , killing wildlife and raising questions about how well the safety of tar sands operations can be assessed. The company extracts bitumen by injecting steam into the tar sands at high pressure to melt the bitumen and push it to the surface.

of the Pembina Institute in Edmonton, Alberta, estimates that the method, known as cyclic steam stimulation, accounts for about 30 per cent of tar sands extraction. There’s nothing inherently risky about cyclic steam stimulation, he says, making these leaks all the more worrisome. “If there are cases like this, it shows things are not as predictable as we might like,” says Severson-Baker.

In January, Canada’s Energy Resources Conservation Board . But investigations by the company and regulator couldn’t determine what had gone wrong. They suggested that the geology of the area was weaker than they had thought and couldn’t contain the pressure from the steam.

The spill could fuel opposition to the controversial Keystone XL pipeline, which would carry oil from this and similar sites. Opponents worry that the pipeline itself has a high risk of leaking, and that increased extraction will exacerbate carbon emissions. US president Barack Obama has said that , and on Saturday he questioned the economic benefits of the pipeline.