A watchdog has found no evidence of bias in how the U.S. Environmental Protection Agency conducted a study on the potential effects of large-scale mining on a world-premier salmon fishery in Alaska's Bristol Bay region.

The inspector general for the EPA released the report that also found no evidence that the agency predetermined the study's outcome.

The report did find that a now-retired EPA employee in Alaska provided comments on a petition from tribes requesting that the agency protect the region from development under the federal Clean Water Act. It found no evidence that any law was violated but said the action may have constituted a misuse of position.

The state and the owner of the proposed Pebble Mine were among those who requested an investigation.