There is a consumption advisory for mountain whitefish near the site of a June train derailment in Stillwater County that spilled oil-based asphalt material into the Yellowstone River.
Montana regulators in a Friday afternoon news release said they sampled several whitefish and found phenanthrene, one of a group of chemicals in substances like oil and plastics, but also in natural formations like shale rock.
Agencies have not yet confirmed the source.
The consumption advisory is in place for mountain whitefish in the Yellowstone River from the Twin Bridges Road railroad bridge to Laurel.
Rainbow trout Montana Fish, Wildlife & Parks sampled came up clear of contaminants. FWP has plans to test more fish species.