Federal investigators said they will seek the cell phone records of two teenagers and a train engineer as they probe whether text messages factored into a fiery commuter train crash that killed 25 people in America's worst rail disaster in 15 years.

The engineer of the Metrolink train that crashed head-on near Chatsworth, California, was chatting with a teenager moments before the crash, the Orange County Register reported Sunday.

Nick Williams, a teenage train enthusiast, told KCBS-TV he exchanged three text messages with engineer Robert Sanchez Friday afternoon. Williams, who considered Sanchez a “mentor,” received the last text at 4:22 p.m., one minute before the train wreck, according to the OCRegister.com report. Williams' claims have not been confirmed.

Investigators from the National Transportation Safety Board are talking to the two 14-year-old teens and their families, Kitty Higgins, an NTSB board member, said at a news conference Sunday.

"There's a lot of things. In any accident I've been involved in, it's never one factor. I call it the perfect storm. We work hard not to jump to conclusions," Higgins said.

She added that the engineer's cell phone was not recovered at the crash site Sunday and declined to say what the teens and their families have told investigators.

"We're going to get the records we need to determine exactly what might have happened here," she said.

Sanchez, who was killed in the crash, said in his final text he would be meeting up with another passenger train later that day.

“I just replied back, 'good deal,' and I just said, 'That's cool,' and I never got a response back," Williams reportedly told CBS2.

Federal investigators also said late Sunday that audio recordings from the train are missing required verbal safety checks between the engineer and the conductor in the seconds before the train collision.

The recordings, obtained by the National Transportation Safety Board from the Metrolink dispatch center, show the engineer and conductor called out and confirmed light signals along the route, but the tapes are missing that call-and-response for the last two lights the train passed just before the fiery wreck, said Kitty Higgins, an NTSB board member.

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Friday night's rail disaster was the nation's deadliest in 15 years, a wreck that killed 25 people and left such a mass of smoldering, twisted metal that it took nearly a day to recover all the bodies.

A preliminary investigation found that "it was a Metrolink engineer that failed to stop at a red signal and that was the probable cause" of the collision with a freight train in Los Angeles' San Fernando Valley, Metrolink spokeswoman Denise Tyrrell said.

"When two trains are in the same place at the same time somebody's made a terrible mistake," said Tyrrell, who was shaking and near tears as she spoke with reporters.

Many of the 25 people killed had been in the front car of the Metrolink train, which was crushed like an accordion in the wreck.

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.

Firefighter Searcy Jackson III, a 20-year veteran and one of the first to pull bodies from the wreckage, said he had never seen such devastation. The 50-year-old said his team pulled one living passenger from the train and cut the mangled metal to remove about a half-dozen bodies.

"We saw bodies where the metal had been pushed together and ... we cut them out piece by piece. They were trapped in the metal," said Jackson, 50, who was back at the scene Saturday afternoon.

Firefighters who extricated the dead from the wreck were rotated in and out of the scene to prevent emotional exhaustion.

"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," fire Capt. Armando 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."

The collision occurred on a horseshoe-shaped section of track in Chatsworth at the west end of the San Fernando Valley, near a 500-foot-long tunnel underneath Stoney Point Park. There is a siding at one end of the tunnel where one train can wait for another to pass.

"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," Tyrrell said. "What we believe happened, barring any new information from the NTSB, is we believe that our engineer failed to stop ... and that was the cause of the accident.

"We don't know how the error happened," she said, adding that Metrolink determined the cause by reviewing dispatch records and computers.

Higgins, of the NTSB, which is leading the probe, said her agency is waiting to complete its investigation before making any statements about the cause of the accident.

Some were puzzled, even dubious, that Metrolink pointed the finger at the engineer so quickly.

"It is a rush to judgment," said Ray Garcia, who until 2006 was a conductor on the same Metrolink 111 train.

Garcia, who now works for Amtrak, ticked off several scenarios in which initial evidence could turn out to be misleading, such as if a central computer showed that a signal was red when on the tracks it was not.

"Just because Metrolink says it was the fault of the engineer, it doesn't mean it's true," said Garcia, who knew the engineer through work. "It's just way too early in the game to point the finger."

Los Angeles County Supervisor and Metrolink board member Don Knabe also said it's premature to blame the engineer.

"There could always be a technical malfunction where ... there was a green light both ways," he said.

A local teenager told CBS2-TV that he had exchanged a brief text message with the engineer shortly before the crash. The station reported that the teen, Nick Williams, was among a group of kids who befriended the engineer and asked him questions about his work.

Tyrrell said before the report aired that she would find it "unbelievable" that an engineer would be text messaging while operating a train. Using a cell phone on duty is against Metrolink rules, former conductor Garcia said.

The NTSB hopes to complete its final report within a year. Tyrrell said Metrolink was stepping ahead of the agency with its findings because "we want to have an honest dialogue with our community."

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.

The Metrolink train, heading from Union Station in downtown Los Angeles to Ventura County, was carrying 220 passengers, one engineer and one conductor when it collided with the Union Pacific freight, with a crew of three, about 4:30 p.m. Friday. It is common in California for freight and commuter trains to use one track.

The crash forced the Metrolink engine well back into the first passenger car, and both toppled over. Two other passenger cars remained upright. The passenger train was believed to have been traveling about 40 mph.

"It's the worst feeling in the world because you know what you're going to find," said fire Capt. Alex Arriola, who had crawled into the bottom of the smashed passenger car. "You have to put aside the fact that it's someone's husband, daughter or friend."

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.

Families of eight of the dead had been notified and two women who were pronounced dead at hospitals were unidentified, coroner's Assistant Chief Ed Winter said.

Authorities released the names of 20 of the victims Saturday. They include Los Angeles police Officer Spree Desha, 35, of Simi Valley, who was riding the train home.

Veronica Gonzalez spent a frantic night and day searching local hospitals for her niece Maria Elena Villalobos before learning she was among the dead.

"She was just the sweetest, kindest, always-trying-to-help-everyone person you would ever meet," Gonzalez said of the 18-year-old, who had just started her first semester at the Fashion Institute of Design & Merchandising in downtown Los Angeles.

Tyrrell, the Metrolink spokeswoman, said the engineer had driven the agency's trains since 1996 and worked for a subcontractor, Veolia, since 1998. She said she didn't know if the engineer ever had any previous problems operating trains or had any disciplinary issues.

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

Garcia, the former Metrolink conductor, said he knew the engineer involved in the crash for nine years and called him qualified and talented.

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, a union representing engineers and conductors, said issues that could factor into the crash investigation could be faulty signals along the track or engineer fatigue.

He said engineers in California are limited to 12 hours a day running a train, although that can be broken up over a stretch as long as 18 hours.

It was not immediately clear how many hours the train's engineer had worked.

Until Friday, Metrolink's worst disaster was on Jan. 26, 2005, in suburban Glendale, where 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.

Friday's train crash was the deadliest since Sept. 22, 1993, when the Sunset Limited, an Amtrak train, plunged off a trestle into a bayou near Mobile, Ala., moments after the trestle was damaged by a towboat; 47 people were killed.

Below is a list of people killed in Friday's Metrolink train disaster and information known about them. Families of two male victims and one female have not been notified and the coroner's office has not released their names. Two other men, one of whom died at a hospital, also have not been identified:

— Christopher Aiken, 38

— Dennis Arnold, 75

— Dean Lafoy Brower, 51

— Alan Lloyd Buckley, 59, a mechanic for the city of Burbank

— Spree Desha, 35, of Simi Valley, Los Angeles Police Department Officer

— Walter Arney Fuller, 54

— Michael Hammersly, 45

— Jacob Hefter, 18, of Palmdale, a student at California State University, Long Beach

— Kari Hsieh, no age given

— Ernest Stephen Kish II, 47

— Gregory Lintner, 48

— Manuel Macias, 31, of Santa Paula, a yoga instructor

— Aida Magdeleno, 19

— Charles Peck, 58

— Howard Barry Pompel, 69

— Donna Remata, 49, of Simi Valley

— Doyle Jay Souser, 56

— Atul Vyas, 20

— Maria Elena Villalobos, 18, of North Park, a student at the Fashion Institute of Design & Merchandising

— Yi Chao, 71