At least 25 people were killed in the head-on crash of a commuter train and a freight train near Los Angeles that officials attributed to the failure of the passenger train engineer to stop at a red light.
The crash, which occurred in the Los Angeles suburb of Chatsworth, was the worst US rail tragedy since 1999.
Los Angeles Mayor Antonio Villaraigosa said the death toll might go higher if people succumb to their injuries at any of the dozen or so hospitals where roughly 47 people remain in critical condition.
About 40 others are in a serious condition.
"We have confirmed 24 dead," said Los Angeles Fire Department spokesman Ron Myers. The collision injured a total of about 135 people.
Officials said 24 people died at the scene and a 25th died yesterday afternoon at a hospital.
"At this moment we must acknowledge that it was a Metrolink engineer that made the error that caused yesterday's accident," Denise Tyrrell, a spokeswoman for the train line, said at a news conference.
She said the engineer, who was not identified, worked for a subcontractor used by Metrolink. He was believed to have died in the crash.
There were 222 people on the Metrolink train, and three Union Pacific employees aboard the freight train, according to media reports.
The force of the crash pushed the locomotive engine pulling the commuter train backward into a passenger car, and both toppled over, igniting in flames. At least seven cars from the freight train derailed, although most remained standing across the tracks.
Both trains were travelling at about 40 miles per hour, according to Tyrrell.
Los Angeles Mayor Antonio Villaraigosa called Friday's collision "a human tragedy that is beyond words."
Metrolink said it will work with the National Transportation Safety Board to complete a thorough investigation of the exact cause of the crash and ensure that everything possible is done to prevent such a tragedy from occurring again.
Federal safety investigators said they had recovered two data recorders from the Metrolink train, and a data and video recorder from the Union Pacific locomotive.
The Los Angeles passenger rail line's previous deadliest crash happened in January 2005, when 11 people were killed after a train slammed into a Jeep Cherokee that had been parked on the tracks. That train derailed, struck another train travelling in the opposite direction and hit a freight train.
The worst crash in the history of Amtrak, the main US rail passenger carrier, occurred on September 22, 1993, near Mobile, Alabama, when 47 passengers and crew died when the train plunged off a bridge that had been damaged by a barge.