VANCOUVER -- Latest update: Developing story here from Monday, June 15.

The operator of the Trans Mountain Pipeline estimates that between 940 and 1,195 barrels of oil were spilled at Sumas Pump Station in Abbotsford, B.C., early Saturday morning.

The company that runs the pipeline says freestanding oil associated with the spill has been recovered, adding that it will continue to monitor groundwater and air quality as cleanup continues.

"We will continue that,” said Ali Hounsell, spokesperson for Trans Mountain. “It’s important to communicate … with area residents, but also important to stress: the readings and information we have from the air monitoring and the groundwater monitoring do not indicate any risk."

A barrel of oil contains roughly 159 litres, meaning roughly 150,000 litres of oil were spilled, at the low end of Trans Mountain's estimate. At the high end, the spill would total 190,000 litres.

Trans Mountain confirmed the spill in a news release Saturday, saying the company had received an alarm early in the morning and immediately shut down the pipeline as crews went to investigate.

"The cause of the incident is under investigation and that will continue,” said Hounsell. “At this time, it’s believed to be a failure of a small-diametre, one-inch piece of pipe."

The spill was contained Saturday, and a cleanup effort has been ongoing ever since.

Both Trans Mountain and the federal Transportation Safety Board have said they are investigating the spill.

The Sumas Pump Station connects the Trans Mountain Pipeline to Washington State via the Trans Mountain Puget Sound Pipeline System, according to the Trans Mountain website.

After shutting down for about 36 hours, the pipeline returned to normal operations Sunday afternoon.

On Sunday, the Union of British Columbia Indian Chiefs (UBCIC) condemned the planned expansion of the Crown-owned pipeline, which moves roughly 300,000 barrels of crude oil per day from Alberta to a terminal in Burnaby, B.C.

Chief Dalton Silver of the Sumas First Nation says his reserve’s drinking water comes from an aquifer beneath the fields where the spill happened, and he wonders what impact it will have.

“With it being on kind of a swampy area, my big concern is seepage into the ground and I’m wondering if people are taking into account the cumulative effects of something like that,” said Silver.

He went on to say this is the fourth time the pipeline has spilled near the reserve in the last 15 years. That is part of the reason the Sumas First Nation is so opposed to the expansion project, he said.

“It’s the direction of my people that we need to oppose this because we’re thinking about the future. What is going to be here when we’re not?”