The water supply of about 69,000 people has been affected by an oil spill in the North Saskatchewan River, the province’s Water Security Agency says.

The spill, which saw between 200,000 and 250,000 litres of crude oil and other material leak into the river Thursday from a Husky Energy pipeline near Maidstone, Sask., has been flowing through the river for the last few days.

North Battleford shut off its water supply intake on Friday; Prince Albert closed its intake Monday morning and later declared a state of emergency; and Melfort has issued a drinking water advisory to take effect at 12:01 a.m. Tuesday. Melfort is also expecting to shut down its water intake when the oil spill reaches the city.

About 45,000 people in the Prince Albert area, 17,000 in the North Battleford area and 7,000 in the Melfort region are affected, according to Sam Ferris, an executive director with Saskatchewan’s Water Security Agency.

Prince Albert has since begun constructing a 20-centimetre-diameter irrigation pipe to draw water from the South Saskatchewan River near the Muskoday First Nation, about 20 to 30 kilometres away, and North Battleford is eyeing plans to install a pipe from Battle River as an alternate source of water.

Precautionary drinking water measures could be in place for weeks or even months in communities affected by the spill, Ferris said.

"It's not going to be a short-term event," he said. "It could go on for some time."

The leak occurred about 300 metres from the shoreline, according to Wes Kotyk with Saskatchewan's Environment Ministry.

About 70,000 litres of an oil-soil mixture have been cleaned up around the source of the leak and another 118,000 litres of oily water has been skimmed from the river. Five booms have been placed on the river with "varied levels of success," Kotyk said.

Husky representatives are not clarifying how long the pipeline was leaking, but say the spill occurred overnight with the line being shut off at about 10:30 Thursday morning.

The company is focused on cleanup right now.

"We're deeply sorry this has happened. We accept full responsibility for the event and for the cleanup and we will make things right," said Al Pate, a Husky vice-president overseeing the response.

The pipeline runs from Husky's heavy oil operations to its facilities in Lloydminster and carries oil mixed with a lighter hydrocarbon, called a diluent, that's added to ease the flow.

Lo Cheng, with the federal Environment and Climate Change Ministry, says its enforcement branch has opened an investigation into whether Husky broke any laws. She also confirmed that some oil sunk below the surface of the river, complicating the cleanup job.

Officials still aren’t sure what caused the leak.

--- with files from The Canadian Press and CTV Saskatoon's Angelina Irinici