A freight train derailed in western Pennsylvania Thursday afternoon leaving several people injured and sending multiple train cars plummeting into an Allegheny River tributary.

The accident happened when the Norfolk Southern train collided with a heavy constriction vehicle that was crossing the tracks near a sewage treatment plant in Harmar Township, outside of Pittsburgh, according to WTAE-TV.

The impact derailed 17 cars, knocking some of them into Little Deer Creek near where it merges with the mighty Allegheny, the station said.

Two train operators and the driver of the construction vehicle were transported from the scene for medical treatment. The severity of their injuries was unclear.

A water line was damaged in the accident and was being repaired, officials told the outlet.

Footage from the scene showed a liquid leaking from the train into the waterway, which a witness said appeared to spill from a pipe that was broken in the incident.