NORTH BERWICK, Maine — An Amtrak train smashed into a tractor-trailer today, causing an explosion that set both on fire and sent flames more than three stories high, a witness and officials said. The truck driver was killed.

Some of the train’s 109 passengers were injured, but it’s not clear how many or how seriously they were hurt. The crash happened at about 11 a.m. in North Berwick, about 40 miles south of Portland.

Tom Gorski, who works in a building 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 with half on each side of the tracks. The ground was littered with debris from the tractor-trailer, which had been hauling a load of trash, he said.

“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.”

There were skid marks on the road leading to the impact, suggesting the driver was trying to stop, Gorski said.

After the impact, the northbound train continued for a half-mile before coming to a stop, officials said. All-terrain vehicles were being used to get the injured passengers from the train to waiting ambulances, McCausland said.

None of the injuries to passengers appeared to be life threatening, Amtrak said.

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.”

The train connects Portland to Boston.