BILLINGS, Mont. (AP) — U.S. government scientists found high levels of pollution that can be toxic to fish, aquatic insects and the birds that feed on them in a river that flows into Montana and Idaho from a coal mining region of Canada, officials said Monday.

Elevated levels of selenium were found in fish and fish eggs from the Kootenai River downstream of Lake Koocanusa.

The lake straddles the Canada border in northwestern Montana and southern British Columbia, and feeds into the Kootenai before the water flows downstream to Idaho.

Selenium is a naturally occurring mineral that can be released into rivers and streams during surface mining. It was absent from water samples taken from tributaries of the Kootenai downstream of the lake, indicating it’s coming from mining-related sources upstream, Environmental Protection Agency hydrologist Jason Gildea said.

No human health impacts were expected from the levels detected in the Kootenai.

High levels of selenium can kill animals and cause them reproductive problems. Animals that lay eggs are most at risk because the pollution accumulates in eggs.