MATTAWAMKEAG — An oil train pulling 15 full 33,000-gallon crude oil tankers apparently spilled only 3 gallons of oil when it derailed Thursday yards from the Penobscot River.

The train went off the tracks near Route 2 and about a few hundred yards from the Winn town line at about 5 a.m. Thirteen of the 15 tankers were found on their sides, Pan Am Railways Executive Vice President Cynthia Scarano said during a phone interview.

“There were no injuries. No leaking,” she said. “There only was a couple of gallons on the ground.”

Two cars and the engine remained upright in the derailment, Mattawamkeag Fire Chief Robert Powers said. About a gallon of oil has come from three of the tipped-over tankers.

“Three gallons — that’s amazing [when you] have the cars laying on their sides, a couple of them in trees,” Powers said. “They’ve built the rail cars to sustain derailment. We are very thankful that that’s where we are at right now.”

Experts at the scene have determined the oil found was spillage from filling the tanks, Scarano said.

“It’s coming from the residue on top just from filling the cars,” Scarano said.

With the large amount of oil in the tankers, local firefighters were joined by Maine Department of Environmental Protection and Maine Department of Transportation crews. The transportation workers came to help Federal Rail Administration investigators determine the accident’s cause, DOT spokesman Ted Talbot said.

“We will follow their lead,” Talbot said. “We are trying to, if we can, identify what went wrong based on what we are seeing now. When the tankers are turned upright and able to move, we will take a second look to see what went wrong.”

Further spillage can occur, Powers said.

“Once the crews get here, we don’t know what will happen once they start trying to upright” them, Powers added.

Firefighters said one of the train’s personnel reported that the first sign of trouble was a sudden increase of speed on the engine.

At about 9 a.m. Thursday, emergency workers were seen gathering along the roadway just south of Markie’s Garage on Route 2. A freight engine pulling three freight cars was stopped along the track about a half-mile south of the scene.

“We’re offloading the cars to tankers so they can be more easily moved,” Scarano said.

What caused the cars to derail is not known but is under investigation, she said.

“That will take a little while,” Scarano said of the probe. “They’ll do a track assessment and review the black box.”

The tankers were filled in Bakken, S.D., and were heading to Canada.

“It’s crude. It goes up there to be refined,” Scarano said.

Railroad workers at the scene referred comment to their Massachusetts office.

Trains pulling tankers northbound to Canada have become a much more common sight along this rail line in the past year as oil drilling operations in the Northwest increase shipments into Canada and overseas.

Mattawamkeag resident Timothy Coombs said he wasn’t surprised to hear of the accident. He and other residents said the track’s heavy use, punishing weather and the track’s degraded condition along some stretches made the accident inevitable.

“It is just something that happens all the time,” Coombs said. “They usually don’t lay on their sides like they did today, but it happens down here four or five times a summer. They usually just derail.”

Several residents said the line of track had been upgraded recently with new timbers placed under the metal rails. Talbot said the tracks had been repaired, but he wasn’t sure to what extent.