CHICAGO (CBS) — Four people reportedly were taken to hospitals after a Metra Rock Island train hit a concrete retaining wall while pulling into the station downtown.

Metra passenger Jack Lavallee said he felt a big jolt when the Rock Island Line train arrived at the LaSalle Street station around 6:30 a.m., and the train hit the metal and concrete end stop.

According to unconfirmed dispatch reports, four people were taken to hospitals with minor injuries. A total of 15 people were treated from the train.

A spokesperson for Metra said the cause of the crash was under investigation Monday morning.

Metra was experiencing a number of problems and delays due to equipment and mechanical problems caused by the cold, including frozen switches.

Also, a Metra train clipped a semi-trailer truck in Niles, at Touhy Avenue, around 6 a.m. That crash caused a 90-minute delay on the Milwaukee District North Line.

Watch & Listen LIVE