Updated

An Amtrak passenger train plowed into the back of a freight train Friday on the South Side of the city, seriously or critically injuring at least five Amtrak employees, fire officials said.

Up to 150 passengers were on the Amtrak train when it came to a "very hard stop," said Fire Department spokesman Larry Langford. None appeared to have suffered serious injuries, but they were being checked out by medical personnel, Langford said.

The Amtrak's three double-decker passenger cars remained upright, officials said, but the engine of the Amtrak train was resting on top of the last car of the freight train.

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Passenger Coert Vanderhill, 60, of Holland, Mich., said the train was traveling at about 15 to 20 mph when the engine, "just ran right up the tail end" of the freight train.

"Everybody just hit the seat in front of them," he said.

Vanderhill, who had come to Chicago to visit his children, had a small cut on his nose and said most passengers, like him, were the "walking wounded."

Passengers, many of them carrying winter coats and luggage, streamed off the trains with the help of rescue workers. Some held the hands of small children. Most passengers walked away from the accident, but some were taken away on stretchers.

Fifteen ambulances and a fire-suppression unit were at the scene tending to passengers, officials said.

Most of the damage was concentrated on the passenger train's engine — where the injured Amtrak employees were riding, officials said. No one was in the portion of the freight train that was struck, Langford said.

"The passenger cars look to be in great shape, great shape," Langford said.

The train was traveling from Grand Rapids, Mich., to Chicago when the accident occurred in a rail yard south of Union Station, Amtrak spokesman Marc Magliari said. Langford said that it was unclear what caused the accident, only that the two trains were on the same track.

The freight train was a Norfolk Southern train en route from Elizabeth, N.J., to Chicago, according to company spokesman Rudy Husband.

Husband said the train had 17 full cars and three empty ones, and that there were only two employees on the train. He said neither was injured.

Husband said he had no details about what caused the accident or what the freight train was carrying.

Passengers were brought to a triage area set up in an empty lot, some on stretchers and backboards.

Graduate student Ariel Hommes, 26, said up until the point of impact, the ride "was very smooth and everyone seemed totally shocked, including the conductors."

Hommes said she was suffering from some soreness in her knees, but when the impact occurred, the seat in front turned toward her, "so I hit the cushion, thank God" instead of a seat back.