By Ethan Lou

(Reuters) - Authorities are building a new containment boom to fight an oil spill in a major western Canadian river, officials said on Saturday, after the spill breached a previous barrier and threatened the drinking water of several communities along the coast.

The city of North Battleford, which draws its drinking water in part from the North Saskatchewan River, shut its supply intake on Friday and switched to using ground water, provincial officials said in a telephone conference with reporters.

Some 1,572 barrels of heavy oil and diluent leaked from Husky Energy Inc's Saskatchewan Gathering System pipeline on Thursday, flowing into the river.

The Calgary-based company has shut the line, stopping the leak, and has been working to contain the spill. It has said it has alternatives ways to move oil and expects "minimal impact."

Husky spokesman Mel Duvall said in a statement the cleanup at the source is "nearing completion."

"A thorough investigation will take place in due course," he said. "There have been no reported impacts to wildlife or aquatic life."

It is not immediately clear what caused the spill, which the province says first appeared some 600 meters (0.3 miles) from the river.

Water levels rose on Friday, pushing debris into the booms upstream from North Battleford, a city of 14,000, and the oil continued to moved downward.

The province of Saskatchewan has started building a new boom near the community of Maymont, about 50 km (31 miles) downstream from North Battleford, though it is not sure when the oil spill will reach it, Wes Kotyk, executive director of environment protection with the province of Saskatchewan, told reporters.

He said the federal environment agency is working on a "trajectory model" to determine the exact size and rate of movement of the oil plume.

Sam Ferris, a provincial water agency official, said authorities are working on plans to deal with water security for communities farther along the river, including Prince Albert, a city with 35,000 people.

Bert West, an official in charge of petroleum and natural gas, said it is too early to talk about cleanup costs or how the incident could potentially affect the economy.

"We haven't have a spill like this, so we're not sure," he said. "As far as costs go, we're not worried about that at this point."

(Reporting by Ethan Lou in Toronto; editing by Diane Craft, Bernard Orr)