The driver of a trash truck who was killed in a collision with the Amtrak Downeaster on July 11 may have been using a cellphone at the time, police said Monday.

The tractor-trailer driven by Peter Barnum, 35, of Farmington, N.H., collided with the northbound Amtrak train, killing him instantly. The train caught fire, and several passengers and crew members sustained minor injuries.

The crash has been investigated by the Maine State Police, local police, Amtrak and the Federal Railroad Administration. The railroad agency said it will be months before its inquiry is complete.

The North Berwick Police Department, which was designated the lead department in the investigation because the crash occurred in that town, concluded that the cause was “driver inattention/distraction by the possible use of a mobile communication device by Mr. Barnum,” according to a news release.

The release does not specify what kind of device Barnum might have been using or why police suspect that he was using one, whether they recovered an intact device at the crash scene or, if it was a cellphone, if they obtained records from the carrier.

An investigative report prepared by a North Berwick police officer and approved Aug. 9 says Barnum disregarded a traffic signal and failed to yield. When noting what might have distracted the driver, if anything, the officer wrote “unknown.”

Monday’s news release, issued by Lt. James Moulton, said the gates and crossing signals on Elm Street were working before the the crash, and that a lengthy skid mark shows Barnum’s efforts to stop.

Moulton said the investigation was a cooperative effort by several police and federal agencies as well as Triumvirate Environmental, the trash-hauling company for whom Barnum was driving.

Amtrak has sued Triumvirate in federal court in Massachusetts for $3 million, which it says is the cost of replacing the Amtrak engine and cars that were damaged in the collision.

Hugh Drummond, a spokesman for Triumvirate, said Monday: “With the pending litigation, the company is not going to have any comment on this today.”

Barnum, hauling 25 tons of trash from Kittery to the incinerator in Biddeford, was headed down a long hill before the crash occurred at 11:05 a.m. He tried to stop the truck, leaving a 75-yard skid mark. The truck’s cab slid around the gates and struck the front of the train, with the force of the crash crushing much of the cab.

The train, consisting of an engine and cars carrying 112 passengers and four railroad employees, would typically have been traveling about 70 mph in that area. The news release does not indicate how fast Barnum was driving when he tried to stop the truck, a 2009 Kenworth that had recently been inspected.

Train traffic will be disrupted Thursday so maintenance workers can repair the section of track where the crash occurred. Trains have continued to run at 30 mph through that area instead of at their usual speed, said Patricia Quinn, executive director of the Northern New England Passenger Rail Authority, which operates the Downeaster.

On Thursday, the two morning trains to Boston will pass the site as usual, then the tracks will be shut down for 10 hours so some ties can be replaced and other improvements made, Quinn said.

“We have not been back up to speed since the incident occurred. This is trying to get that track back up so we can go at operating speed,” she said.

The work should be complete by the time the 5:40 p.m. train heads north out of Boston.

Train riders whose routes are disrupted by the track work will be able to take buses, she said. 

Staff Writer David Hench can be contacted at 791-6327 or at: [email protected]