Two people on the train, including the engineer, who is in critical condition, were hospitalized at Arrowhead Regional Medical Center.
The westbound Union Pacific train struck a slower-moving train in the Fontana at about 11:55 p.m. Thursday, San Bernardino County fire spokesman Maurice Moore said. Several cars derailed and the locomotive wound up on top of a freight car. The slower freight train was hauling I-beams that pierced the locomotive of the faster train, trapping the engineer, Moore said.
Firefighters were unable to get the trapped engineer out of the wrecked Union Pacific locomotive and a surgical team was called in to amputate his arm, Moore said. The engineer is expected to survive.
The other hospitalized railroad worker had moderate injuries.
The speed of the trains wasn't known. Calls to Union Pacific spokesman Aaron Hunt weren't immediately returned.
The wreck alongside eastbound lanes of Interstate 10 at Cherry Avenue created a traffic crush for more than four hours.
Emergency vehicles used the freeway to access the wreckage and it was feared hazardous materials might be leaking from a rail tanker, Moore said. It was later determined there were no dangerous materials in the wreckage.
Eastbound freeway lanes reopened by 4 a.m. Friday.