Police questioned a passenger on a small commercial plane that flew from Chicago to a northern Michigan resort town on Friday after the crew reported he was acting suspiciously.

Crew members aboard United Airlines Flight 6036 said the 28-year-old California man had taken "an article" into the bathroom and left without it, said Traverse City Police Capt. Steve Morgan. The crew found that a panel inside the bathroom had been tampered with, he said.

They requested law enforcement assistance while approaching Cherry Capital Airport, Morgan said.

A government official said earlier the passenger had made a bomb threat, but Morgan said there was no bomb threat. A bomb sniffing dog was called in to sweep the aircraft and luggage and nothing was found, he said.

The passenger was being questioned Friday afternoon by local police and the FBI but had not been arrested or charged, Morgan said.

"He's been cooperative throughout," he said.

Passenger David Boyer, 47, a Chicago attorney who has a home near Traverse City, said he was seated seven rows behind the man, who got up and went to the bathroom, stayed about five minutes and then sat back down. Boyer said there was no disturbance and no reason to believe anything was wrong until the plane landed.

Police came aboard and took the man off the plane. He was cooperative and didn't put up a struggle, Boyer said. The passengers were then taken to the airport fire department building where they were questioned by authorities, he said.

"Everything's fine. It's just a hair-trigger misunderstanding as far as I'm concerned. It's a non-event. It was a completely routine flight," Boyer said as he was walking toward the terminal from the parking lot.

The incident comes as airlines and airports have boosted security in the wake of the failed attack on a packed Detroit-bound Northwest Airlines flight on Christmas. A Nigerian man, Umar Farouk Abdulmutallab, has pleaded not guilty to charges he tried to blow up the plane using a chemical-laden device.

Friday's United Airlines flight was operated by St. George, Utah-based SkyWest Inc., the holding company for SkyWest Airlines. The medium-sized, twin-engine Bombardier CRJ-200 passenger plane had 11 passengers and three crew members on board, said Marissa Snow, a SkyWest spokesman.

United Airlines spokeswoman Sarah Massier said there was a "disruptive passenger" on the flight that departed from O'Hare International Airport in Chicago. She said the flight crew requested that law enforcement officials meet the flight once it landed but would not provide more details.

Cherry Capital suspended operations for about 30 minutes, delaying the arrival of one plane and the departure of another by about 20 minutes, airport flight manager Ron Hubbard said.