The Canadian National Energy Board, which has headquarters in Alberta, said there was no threat to the public near Merritt, British Columbia, from the spill. The pipeline is operated by Kinder Morgan and was expanded in 2008.
The NEB said it received an incident report earlier this week but has yet to determine the size of the spill. The Vancouver Sun reports less than 20 barrels of oil were released.
"The pipeline has been shut down to prevent additional oil from being released into the environment and the company is currently in the process of contacting area residents," the regulator said in a Thursday statement.
NEB reported a similar release this week near the St. Clair River in Ontario.
Former British Columbia Environment Minister Barry Penner told the newspaper oil issues were testing the public's patience.
"I think when it comes to public opinion now, any spill is one spill too many," he said.
The provincial government has expressed concern about pipeline expansion projects in the region. Any spills in the region would harm the pristine environment and create long-term problems for aboriginal communities, it says.