A morning collision between two Chicago trains left dozens of commuters injured during rush hour on Monday, authorities say.

Two Chicago Transit Authority trains slammed into one another in Forest Park, Illinois–just outside of Chicago–between 7:30 and 8 a.m., crushing part of at least one train car and sending several people to local hospitals. Officials say none of the injuries have been life-threatening, but an investigation is underway to determine what caused the collision.

Although the CTA is currently treating the wreck as an accident, Forest Park Mayor Anthony Calderone says that no one was at the controls inside one of the trains, which only had four cars; morning trains usually have several cars, which has raised suspicion that perhaps the train was hijacked. Police are reportedly treating the area as a crime scene.

Robert Kelly of Amalgamated Transit Union 308 said that a key would have been needed for the train to be taken; he also confirmed that it was moving between 20 and 25 miles per hour when it slammed into a westbound train that was sitting stationary on the tracks.

Blue Line trains not stopping at Harlem (Forest Park br.) due to an incident involving a train. Again, service has resumed to Forest Park.

— cta (@cta) September 30, 2013

Image: WSOC