LOS ANGELES (AP) _ The death toll in the collision of a Metrolink train and a freight train reached 25 Saturday, and the commuter passenger service announced that a preliminary investigation determined that its own engineer failed to stop at a red light.

The search for victims ended Saturday afternoon, nearly a full day after emergency crews first responded to the deadliest U.S. rail accident in 15 years.

‘It was a very, very difficult operation,’ Mayor Antonio Villaraigosa said. ‘It was like peeling an onion to find all the victims there.’

A Metrolink train, heading from downtown Los Angeles to Ventura County on Friday afternoon, was carrying 220 passengers, one engineer and one conductor when it collided with the Union Pacific freight, with a crew of three.

Villaraigosa said the death toll could continue to increase because dozens of passengers remained hospitalized in serious or critical condition. He also complimented emergency crews that worked nearly 24 hours to rescue passengers and pull out bodies.

‘The dignity they gave the dying made you well up with tears, made you feel a sense of pride,’ he said.

The National Transportation Safety Board was continuing what promised to be a lengthy investigation into the cause of the collision.

Before NTSB gave any public comment on the probe, a Metrolink spokeswoman said it appeared a Metrolink engineer either did not see or disregarded a red light that could have prevented the collision.

‘Even if the train is on the main track, it must go through a series of signals and each one of the signals must be obeyed,’ Metrolink spokeswoman Denise Tyrrell said. ‘What we believe happened, barring any new information from the NTSB, is we believe that our engineer failed to stop.’

NTSB board member Kitty Higgins said the agency had not ruled out Metrolink’s theory of human error but was waiting to complete its investigation before making any statements about the cause of the accident.

‘We know what happened. … These trains collided, but we don’t know why it happened and it’s our job to find out,’ Higgins said.

Tyrrell said the engineer worked for a subcontractor, Veolia, and had driven Metrolink trains since 1996. She said she believes the engineer, whose name was not released, was killed.

A total of 135 people were injured, with 81 transported to hospitals in serious or critical condition. There was no overall condition update available Saturday, but a telephone survey of five hospitals found nine of 34 patients still critical. Many were described as having crush injuries.

The only victim officially identified was Los Angeles police Officer Spree Desha, 35, of Simi Valley, who was riding the train home.

‘She sat in the first train (car) as a matter of practice, in uniform, so if someone came on the train and made trouble, she was ready to help out. … That was just the way she did business,’ said Jim McDonnell, first assistant chief for the Los Angeles Police Department.

Police set up what they called a unification center at a local high school to try to connect worried people with information about friends or relatives who they believed were aboard the train.

The Los Angeles County Department of Health also scheduled counseling services for Monday for passengers and their families.

Before the search ended, firefighters were being rotated in and out of the scene to prevent emotional exhaustion, Hogan said.

‘There are some things we are trained for, there are some things I don’t care what kind of training you have, you don’t always prepare for,’ Hogan said. ‘This situation, particularly early on, with people inside the train, with the injuries, and with people moaning and crying and screaming, it was a traumatic experience.’

NTSB, the leader of the probe, announced Saturday it will interview survivors and Metrolink officials and hopes to complete its final report on the accident within a year.

Higgins said rescue crews on Saturday recovered two data recorders from the Metrolink train and one data recorder and one video recorder from the freight train. The video has pictures from forward-looking cameras, and the data recorders have information on speed, braking patterns and whether the horn was used.

Tyrrell said she didn’t know if the engineer ever had any problems operating trains or had any disciplinary issues.

‘When two trains are in the same place at the same time somebody’s made a terrible mistake,’ she said.

Ray Garcia, a train conductor with Metrolink until 2006, said he knew the engineer involved in the crash for nine years and called him qualified and talented. He declined to name the engineer.

‘I’m very sad that that happened,’ Garcia said. ‘It’s terrible.’

Garcia said he knows the stretch of track where the collision occurred and believes engineers are warned twice with yellow lights before reaching a red light at the end of a siding.

Tim Smith, state chairman of the Brotherhood of Locomotive Engineers and Trainmen, said issues that could factor into the crash investigation could be faulty signals along the track or engineer fatigue.

‘We’ve seen some signal anomalies of late. I’m always suspicious of that,’ Smith said.

He said engineers can be on duty up to 18 hours a day, with breaks, though they are legally limited to 12 hours a day running a train.

‘Doing that for five or six days in a row, you have the cumulative fatigue factor that becomes are real bear,’ he said.

It was not immediately clear how many hours the train’s engineer and conductor had worked.

The collision occurred on a horseshoe-shaped section of track in Chatsworth at the west end of the San Fernando Valley.

The crash forced the Metrolink engine well back into the first passenger car, and both toppled over. Two other passenger cars remained upright.

Tyrrell, visibly shaking and appearing near tears as she spoke with reporters, said Metrolink determined the cause of the crash by pouring through dispatch records and reviewing computers.

Veolia issued a statement Saturday calling the collision a ‘tragic incident.’ The company said it is cooperating with NTSB’s investigation.

Metrolink launched its service in Southern California in 1992. More than 45,000 commuters board Metrolink trains weekdays in Los Angeles, Ventura, Orange, Riverside and San Bernardino counties.

In 2002, a freight train hit a Metrolink train in Placentia, killing three people and injuring more than 260.

Until Friday, the worst disaster in Metrolink’s history occurred on Jan. 26, 2005, in suburban Glendale when a man parked a gasoline-soaked SUV on railroad tracks. A Metrolink train struck the SUV and derailed, striking another Metrolink train traveling the other way, killing 11 people and injuring about 180 others. Juan Alvarez was convicted this year of murder for causing the crash.

That was the worst U.S. rail tragedy since March 15, 1999, when an Amtrak train hit a truck and derailed near Bourbonnais, Ill., killing 11 people and injuring more than 100.

The Sunset Limited was involved in the worst accident in Amtrak’s 28-year history. On Sept. 22, 1993, 42 passengers and five crew members died when the train plunged off a trestle into a bayou near Mobile, Ala. The trestle had been damaged minutes earlier by a towboat.