(Reuters) - Two Chicago Transit Authority trains collided in a western suburb of Chicago during Monday morning's rush hour, resulting in 33 injuries, the agency reported.

The incident happened at the Harlem Station in Forest Park, Illinois, west of Chicago. One train was standing at the station at the time of the accident at 7:45 a.m. local time, according to CTA spokeswoman Catherine Hosinski. The cause is under investigation.