NEW MILFORD — Railroad crews worked most of Monday trying to right a derailed freight train on the tracks as investigators looked for the cause of the weekend accident.

Seven cars were involved in the derailment in the Gaylordsville section of New Milford. A Housatonic Railroad Co. official said most of the cars slipped slightly off the tracks and were not seriously damaged.

“Most of them were empty, so it wasn’t really an issue,” said Matthew Whitney, an associate general counsel for the railroad.

No one was injured in the accident and the train was not carrying hazardous materials, Whitney said.

The train had left Danbury and was heading to Pittsfield, Mass., when it derailed at a private crossing off River Road, near Riverview Road, about 1 a.m. Saturday.

Whitney said the accident was “very minor” and the train was expected to be back in service on Monday.

Police are not involved in the investigation, but they said the railroad notified them about the accident.

New Milford Mayor David Gronbach said he was told over the weekend the cause of the accident was a broken rail in the crossing.

This is the second trail derailment in New Milford in two years.

In February 2014, an engine pulling a freight train derailed near Boardman Road. The accident was blamed on ice that had built up in the crossing at Sostak Road and dislodged the engine’s wheels from the track. No one was injured in that crash.

Whitney described Saturday’s derailment as an isolated incident, noting the tracks in New Milford have not been a problem.

Police Lt. William Scribner agreed. He said this may be the third train derailment in town in about 20 years.

The Housatonic Railroad Co. ended its passenger service in 1971 and reopened for freight service in 1983., 203-731-3411, @olivnelson