Federal officials are investigating claims that drones have been flying around the BP Cherry Point Refinery in violation of U.S. law.

“We are aware of reports of unmanned aerial vehicle activity in Whatcom County and are in contact with our partners to determine if any action by law enforcement is warranted,” the FBI’s Amy Alexander told The Bellingham Herald in an email on Thursday.

No additional information could be provided, Alexander said.

A U.S. Customs and Border Protection official told The Herald that the FBI is investigating. The Department of Homeland Security didn’t immediately respond to The Herald’s request for comment.