Plains Midstream Canada says in a news release that early indications suggest the Kemp line in northwestern Alberta suffered "external damage" before releasing condensates from natural gas production late last week.
The company has said preliminary estimates suggest approximately 950 barrels were released over an area about 1.5 hectares.
It says more than 60 people are working to clean up the spill.
The news release doesn't specify what the construction equipment was doing near the pipeline or whether it was associated with the pipeline's operation or maintenance, and no one from the company could be immediately reached to elaborate.
The Plains Midstream news release says it has conducted an assessment that has found no effect to wildlife.
"We regret this incident and are working around the clock to limit the impact of the release," said Stephen Bart, the company's vice president of crude oil operations, in an earlier news release.
"Industry-leading technical experts and regulatory bodies are engaged onsite in our response efforts and to ensure an effective cleanup."
Cara Tobin, a spokesperson for Alberta's energy regulator, said the regulator's staff have been at the scene of the spill since the company detected and reported it on Friday.
Tobin said the spill was in a remote location and was detected by electronic sensors within the pipeline itself. She said it wasn't near any flowing water and hadn't reached any rivers.
"There's no public impact although there are First Nations in the area. The company has attempted to contact them," Tobin said Sunday, although she didn't know if those efforts had been successful.
The leak follows another Alberta pipeline spill in recent weeks that saw 9.5 million litres of industrial waste water flow into a wetland near the community of Zama City.
Aboriginals in the area have said all vegetation in the spill area, from grass to trees, is dead but a spokesman from the pipeline's owner, Apache Canada, said 99 per cent of the fluid was water and that wildlife doesn't seem to have been affected.
Apache is still investigating the cause of the leak.
Earlier this year, Plains Midstream was charged under Alberta's Environmental Protection and Enhancement Act following an April 2011 pipeline breach northeast of Peace River. The breach spilled 4.5 million litres of oil and was blamed for powerful smells in the community of Little Buffalo that residents said caused headaches and stomach problems and kept schoolchildren at home for days.
That case is scheduled to be in provincial court in Peace River on Monday.
Another Plains Midstream breach in June 2012 leaked up to 475,000 litres of oil into the Red Deer River near Sundre in central Alberta.
Greenpeace Canada said the most recent spill near Manning makes it obvious the government and its energy regulator are failing.
"We need a truly independent system so that protecting industries image so the government can push more tar sands pipelines doesn't continue to be more important than protecting the public good," spokesman Mike Hudema said in a news release.
Plains Midstream Canada says the Kemp pipeline remains shut and that sections of it are being removed and will be inspected by a third-party firm.
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