At least a dozen people suffered injuries and have been taken to area hospitals after two commuter trains collided, with one derailing, at Chicago’s Union Station, city emergency officials said Friday morning.

A spokesman for the Chicago Fire Department says one of the trains derailed, but he didn’t have any details. Metra spokesman Tom Miller says the collision occurred at about 8:15 a.m. Friday, but that to his knowledge no trains derailed. The crash involved a Burlington Northern commuter train from Aurora and an Amtrak train heading to Carbondale.

Spokesmen for the rail lines and the fire department say the two trains collided as a train on Metra’s Burlington Northern line was coming into the station and the Amtrak train was leaving for Carbondale at about 8:15 a.m.

There was initial confusion about the location of the crash, with first responders arriving just north of the crash, which occurred under the Old Chicago Main Post Office on Congress Parkway.

Passengers, some complaining of head and neck injuries, had to evacuate through tunnels spanning almost four blocks.  Officials said at least one person may have broken ribs and that there were two pregnant women that were in stable condition.

Metra board member Jack Schaffer was on the scene when a Metra train collided with a truck last month in suburban Mount Prospect. He said, “The train on train accident is unusual. Although I will tell you and I say this with some reluctance, we still are on high alert out for terrorism.”

Spokesmen for both lines would not comment on which train caused the collision.

An investigation is underway.

—The Associated Press contributed to this article.