WILLISTON, N.D. — Authorities say a flight attendant accused of disrupting a flight from Denver to North Dakota was drunk.

Police in Williston, in northwestern North Dakota, say they received a call from airport officials before the Trans State Airlines flight landed Thursday afternoon that an occupant was intoxicated and had a medical condition. Police determined that the person was drunk and forwarded the investigation to the FBI.

No further details have been released. A passenger tweeted that one boarding announcement was, “If your seatbelt isn’t tight, you (expletive) up.”

Trans States Airlines, a regional service provider for United Airlines, said reports of erratic behavior are being investigated and the flight attendant is being held off the job.

United Airlines said it is refunding air fare for passengers “as a gesture of goodwill.”