A commuter jet on its way from Minneapolis to Grand Forks, N.D., was diverted to Fargo after a flight attendant thought a passenger tampered with a fire extinguisher in the jet's lavatory and left some suspicious putty-like material in the lavatory's waste container.

After noticing that a male passenger was behaving in what she deemed a suspicious manner, a flight attendant on Pinnacle Airlines Flight 4375 decided to check the lavatory after he emerged. She found that the fire extinguisher was not in its proper place, according to a Pinnacle spokesman. The flight attendant also spotted some putty-like material that she feared might be explosive, but it was later found to be harmless.

The attendant notified the pilot, who diverted the flight to Fargo, where it landed without incident at 10 a.m. Sunday, authorities said.

The suspicious passenger was interviewed by the FBI and local law enforcement officials before being released. No charges resulted from the incident. Authorities declined to name the man.

The jet was carrying 20 passengers and three crew members. It was moved to a remote location, where it was swept for suspicious items with "negative results," meaning it was deemed safe to fly, according to a statement from the Transportation Security Administration.

"There was activity that got [the flight attendant's] attention prior to him going into the bathroom that caused her to want to investigate," said Eric Epperson, a Pinnacle spokesman. "She went in behind him to look around."

Authorities had no information on the putty-like material, except to say it wasn't explosive. "It turned out not to be what they thought it was," said Meara McLaughlin, a vice president with FlightStats, a Portland, Ore.-based provider of real-time flight information.

As the plane was being diverted, passengers were not told on board of the reports of suspicious activity. They were interviewed by local law enforcement officials and then taken by bus to Grand Forks International Airport.

Chris Serres • 612-673-4308