The Southeastern Pennsylvania Transportation Authority said the crash happened around 12:15 a.m. Tuesday.
An inbound Norristown High Speed Line train crashed into an unoccupied, parked train at the 69th Street Terminal in Upper Darby, said SEPTA spokeswoman Heather Redfern.
SEPTA said 42 people aboard the train were injured. All injuries were described as non-life threatening.
In an early morning news briefing, Upper Darby Mayor Nicholas Micozzie said at least four people suffered serious injuries. The victims were taken to area hospitals.
"The conductor is in the hospital right now, I can't release his condition," Micozzie said.
One passenger told reporters at the scene that the operator of the train was "all banged up." The passenger said "there was blood everywhere."
The cause of the crash remained under investigation.
SEPTA said there likely would be service disruptions for the Tuesday morning commute.
In February, four people were injured in a crash near the 69th Street Terminal involving three out-of-service commuter trains. At the time, SEPTA said one train rear-ended another on a loop where trains turn around to get back into service. Cars from that accident derailed and hit a third train on nearby tracks.
The Associated Press contributed to this report.
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