NORTH BERWICK, Maine — An Amtrak train traveling at 70 mph smashed into a tractor-trailer Monday in a fiery collision that killed the truck driver, injured a half-dozen others and sent flames more than three stories high, a witness and officials said.

The trucker was identified as 35-year-old Peter Barnum of Farmington, N.H.

Witnesses reported that safety lights were flashing and gates were down at the intersection when the tractor-trailer crossed into the path of Amtrak’s Downeaster at about 11 a.m., said Police Chief Stephen Peasley. None of the train’s 112 passengers or three crew members suffered life-threatening injuries.

Workers cleared equipment and debris from the tracks, allowing the train to return to service about 12 hours after the accident.

Amtrak announced Monday night that service was being restored with the final run of the day from Boston to Portland.

One witness said the tractor-trailer driver slammed on the brakes, Peasley said. “From what I’ve been told, it appears that it skidded through the intersection,” he said.

There were about 200 feet of skidmarks on the road leading to where the crash occurred, and the truck apparently clipped one of the gates before the collision, said Stephen McCausland, spokesman for the Maine Department of Public Safety.

Tom Gorski, who works in a building about 50 yards from the intersection, said he heard the approaching locomotive, then a massive boom that shook the building. He said he ran to the scene, where the truck’s cab was split into pieces.

“It looked like somebody dropped a bomb. The flames were shooting higher than a three-story house,” said Gorski. “It brings tears to your eyes.”

After the impact, the northbound train dragged the truck’s cab about 200 yards, then the train continued on before coming to a stop, said Deputy Fire Chief Larry Straffin.

The train’s engineer hopped off the locomotive, separated the burning engine from the passenger cars and moved the engine down the tracks to keep the flames from spreading, Straffin said. Firefighters had to drag hose down the train tracks to douse the fire to the locomotive, he said.

The tractor-trailer was carrying a load of trash, which was strewn in heaping piles alongside the train tracks.

The locomotive was totally charred after the fire was extinguished, obscuring its markings, said Brianna Bataran, 17, of North Berwick. “You couldn’t even tell what kind of train it was.”

Six people on the train — four passengers and two crew members — suffered injuries, said Patricia Quinn, executive director of the Northern New England Passenger Rail Authority.

Three were taken to a hospital in Sanford, where two were being treated for smoke inhalation and the third for a head injury, before being released, a spokeswoman said.

Barnu was ejected from the truck. He was working for Triumvirate Environmental Inc., a trucking company based in Massachusetts, McCausland said.

The company issued a statement saying it was cooperating with investigators.

“The safety and well-being of our employees is Triumvirate Environmental’s top priority and we are cooperating fully with local authorities as they conduct their investigation,” the statement said.

Service on the route was delayed after the collision, and the passengers completed the trip to Portland by bus. Amtrak will use a combination of trains and buses until service is restored, possibly Tuesday morning. Nearly 1,400 passengers a day ride the Portland-to-Boston service.

Last month, a man drove a semi-trailer into the side of a passenger train in Nevada in a fiery crash that killed six and injured more than 20. Amtrak is suing the Nevada trucking company the man worked for, alleging negligence in its training.

Associated Press writer David Sharp in Portland, Maine, contributed to this report.