(Reuters) - A one-car commuter train slammed into an unoccupied parked train car at a station near Philadelphia on Tuesday, injuring 33 people, a National Transportation Safety Board official said.

The railcar hit the vacant parked car at the 69th Street Terminal in Upper Darby, 10 miles west of Philadelphia, around 12:15 a.m. EDT as it pulled into the station, said Heather Redfern, a spokeswoman for the Southeastern Pennsylvania Transportation Authority (SEPTA).

Some 42 passengers were on the railcar that was moving. Earlier on Tuesday, officials said that 42 people had been injured, but at a press conference on Tuesday evening National Transportation Safety Board Rail Investigator Ruben Payan said 32 passengers and the train’s operator had been injured.

Payan said the agency’s investigation was only beginning and that it may be up to a year before a final report was issued on the incident. He said team of investigators would be at the scene for four to five days.

“The injuries appeared to be non-life threatening for all passengers and the operator,” Redfern said. “It’s all under investigation at this point.”

The train’s operator was released from a hospital earlier on Tuesday and was expected to speak with NTSB investigators on Wednesday, Payan said.

Upper Darby Mayor Thomas Micozzie told reporters that at least four people were being treated at area hospitals.

In February, four people were injured when a train rear-ended another near the 69th Street Terminal. Eight people were killed and more than 180 injured when an Amtrak train derailed in Philadelphia in 2015.