The night before an oil spill was detected in the North Saskatchewan River, Husky Energy was alerted to “pressure anomalies” in the pipeline system, but a leak was not identified until the next morning, according to the company.

An incident report filed with the Saskatchewan government said a “pipeline release” was discovered on the south shore of the North Saskatchewan River at 8 p.m. on July 20, raising questions about why Husky crews were dispatched only the next morning, as initially reported.

But in an email sent to CTV News on Tuesday, a Husky Energy spokesperson said the company did send out crews on July 20 after “the pipeline monitoring system indicated pressure anomalies.” The anomalies were noted as the pipeline system was being returned to service -- a “common” occurrence during startup operations, the company said.

“As a precaution, crews were dispatched along the gathering system and did not identify a leak,” Mel Duvall, the media and issues manager for Husky Energy, said in a statement.

“As our analysis continued through the night, we decided as a further precaution to start safe shut down procedures at about 6 a.m. The valves on either side of the river shut in automatically as a part of the shutdown procedures,” she said. “Subsequently, on Thursday morning we received reports regarding a sheen on the river.”

The company then initiated its emergency response plan and dispatched crews to the spill site, Duvall said.

The company provided that sequence of events after a Husky executive evaded direct questions about the timing of the oil spill during a media conference call on Tuesday.

Al Pate, Husky’s vice-president overseeing the spill response, acknowledged that the company was aware of some sort of “irregularity” with the pipeline on July 20. But he avoided repeated questions from reporters about when the actual leak was first detected, saying the exact timeline will be part of a “comprehensive” investigation into the spill.

The pipeline leaked an estimated 200,000 to 250,000 litres of oil and oil-thinning chemicals into the North Saskatchewan Rivernear Maidstone, Sask., before it was shut off on Thursday.

Pate repeated the company’s apology for the leak and said Husky has set up an emergency hotline for claims related to the oil spill. The toll-free number is 1-844-461-7991.

“We take full responsibility for what’s happened and we want to make it right,” he said.

The spill has left a number of communities scrambling to protect their water supplies or find alternative sources, as the oil slick makes its way down the river.

On Friday, the community of North Battleford stopped drawing water from the river and turned to well water instead.

As of 6 a.m. Monday, the city of Prince Albert only had a 48-hour water supply after the city also stopped drawing water from the river.

Prince Albert city manager Jim Toye told CTV News Channel Tuesday morning that a storm detention pond could provide water for the community for another four to five days, but it has to be treated first.

Construction on a long water pipe that can draw water from the South Saskatchewan River should be completed on Wednesday, Toye said.

Prince Albert has declared a state of emergency and banned most outdoor use of water. 

“The people have been very understanding,” Toye said.

In the meantime, a precautionary boil-water advisory has been issued for Melfort and other nearby communities in east-central Saskatchewan.

A spokesperson for Saskatchewan's Water Security agency says a precautionary drinking order could be place for weeks or even months because of the spill. The agency estimates that the water supplies of close to 70,000 people have been affected so far.

With files from The Canadian Press