A commuter train hit another one in a downtown tunnel at the beginning of the evening rush hour Monday, slightly injuring nearly three dozen people, a transit spokesman said.

Gary Fairfax, a spokesman for the Southeastern Pennsylvania Transportation Authority, told The Philadelphia Inquirer he did not know whether both trains were moving. If so, neither was going fast, he said.

"Even though the speed was slow, these trains are so large that the impact that is transmitted can bruise you and bang you up a little bit," said another SEPTA spokesman, James Jordan.

Fairfax said 35 people suffered minor injuries.

The accident involved a train bound for Norristown and a train headed for Doylestown, Fairfax said.

The trains went on to the next stop so passengers would not have to evacuate in the tunnel and because the stop was near Temple University Hospital.

A nursing supervisor said that a dozen people were treated and that four were admitted, including one to the intensive care unit for observation after reporting tingling in the fingers.

"Trains are never under any circumstances supposed to be close enough to make contact so we take that very seriously and will be investigating that very seriously," Jordan said.

The accident caused train delays of about 20 minutes, officials said.