A pipeline leak discovered Wednesday in Alberta has spilled 31,500 barrels of emulsion - petroleum mixed with sand and water - but has not contaminated any bodies of water, Canadian officials have confirmed.

According to the Alberta Energy Regulator (AER), which has responded to the spill, the release has not flowed into a waterbody.

“My understanding is that the pipeline and pad site had been isolated and shut-in earlier today, effectively stopping the source of the release”, said Murchland, Alberta Energy Regulator’s public affairs manager, to CBC News.

Nexen spokesman Kyle Glennie said the company is investigating how long the pipeline was leaking before it was shut off.

Notley, who on Friday finalised a Canadian energy strategy with other provincial leaders, also said the leak did not shake the conclusion that pipelines are the safest way to move hydrocarbon products.

This is Alberta’s fourth large spill in recent years. Numerous accidents are the result of the increasing supply and demand for oil transport through pipelines that are now used at full capacity unceasingly to keep pace with production.

The site is located about 35 kilometres southeast of Fort McMurray.

“We sincerely apologize for the impact this had caused”, he said Friday.

The regulator has sent investigators to Long Lake to try to determine the cause of the pipeline failure.

With pipeline integrity one of the issues at the heart of the national discussion about the future growth of the oilsands - along with global climate change - the timing for what is one of the largest spills by the oil industry in Alberta could hardly have been worse.

Greenpeace, meanwhile, said the spill was just the latest evidence of environmental risks posed by the controversial practice of extracting oil from tar sands.

Alberta Premier Rachel Notley called the pipeline break “very troubling”.

“What we need to do is have a rigorous and fulsome investigation into what went wrong here and ensure it is sufficiently rigorous that it can produce clear, meaningful recommendations to ensure that it doesn’t happen again”, she said.

On Thursday, Nexen said the spill had been contained - steps confirmed by AER Friday. “Unfortunately, there’s nothing we can say except that we are going to learn from this”.

She said it was premature to talk about penalties and enforcement.