A crash between two trains on Chicago's blue line has sent at least 33 people to the hospital has created a mystery: how did the second train involved get there?


Two trains after collision in Chicago (WMAQ TV)

An eastbound train hit a westbound train that was stopped on the same track at the Harlem station in Forest Park, about 10 miles west of downtown Chicago. WMAQ TV reports that one of the one of the trains had been taken from a rail yard called "The Jungle" without permission and that the area is being treated as a crime scene.

However, Forest Park Mayor Anthony Calderone tells WLS TV there was "no human being on that eastbound train." ATU local 308 President Robert Kelly calls the situation "baffling"  and that trains in a rail yard should not be able to be moved.

"We don't know what led the train to start moving on the path it did. It should not have done so," CTA spokesperson Brian Steele told WLS TV." There's no indication at this point that this was criminal activity. There were no broken windows or pried open doors on the CTA train.

The National Transportation Safety Board is sending a team to investigate.

CTA spokeswoman Lambrini Lukidis says 33 people suffered non-life threatening injuries. Calderone says he was told as many as four dozen people were injured, most reporting back and neck pain. He says they were taken to local hospitals.

A number of emergency crews have responded to the scene which has shut down a portion of the Blue Line according to WLS TV.

This is a breaking story. Check back for additional information.