Officials of the California commuter rail system Metrolink say Friday's deadly train crash outside Los Angeles, which killed 25 people and injured 135, was caused by an engineer who failed to stop at a signal. Mike O'Sullivan reports that the day after the crash, emergency workers were still searching for victims, but holding out little hope of finding survivors.

Rescue and recovery work continues as darkness begins to fall after a commuter train collided with a freight train in the Chatsworth area of Los Angeles, 12 Sept. 2008

The website of the Metrolink commuter rail system says human error or a signal failure on the part of Metrolink may have played a role in the crash of the commuter train with a freight train operated by the Union Pacific Corporation. A Metrolink spokeswoman was more direct. She said Saturday that a preliminary investigation showed an engineer employed by a Metrolink subcontractor, Veolia Transportation, failed to stop at a red signal.

Workers continued to search for victims in the wreckage, but said the chance of finding more survivors was remote. Kitty Higgins of the National Transportation Safety Board called the crash one of the worst train accidents her agency has seen. She said data recorders retrieved from the crash site should yield important information.

"We will learn a lot from the data recorders from both trains. We will hopefully be able to interview the crewmembers, other witnesses. That will all contribute to our fuller knowledge of exactly why this happened."

The Metrolink train was crowded with more than 200 commuters when the trains collided head-on on a section of single track late Friday afternoon. The crash forced the engine of the commuter train back into the first passenger car, and both toppled on their side. Two other passenger cars remained upright.

As the death toll mounted, Los Angeles Deputy Fire Chief Mario Rueda said the round-the-clock effort is taking a toll on emergency workers.

"As you can imagine with the wreckage, it's been very, very difficult for fire fighters and police officers. They've just done a great job. I'm very proud of them."

The first victim to be publicly identified was a female police officer who was riding the train home.