LOS ANGELES — Federal investigators today combed railroad tracks and crushed wreckage looking for evidence to explain the America’s deadliest rail disaster in 15 years and made plans to interview dispatchers.

At the same time, a National Transportation Safety Board spokesman downplayed a report that the engineer of the Metrolink commuter train had sent a text message shortly before Friday’s accident, in which 25 people were killed and 135 were injured when the Metrolink train slammed into an oncoming Union Pacific freight engine on the same track at 40 mph (64 kph).

A Metrolink spokeswoman, Denise Tyrrell, had already said the commuter train’s engineer was at fault because he failed to stop at a red light on the tracks — but NTSB board members cautioned that they had not completed their investigation.

Eleven NTSB investigators were working on the accident puzzle, an agency spokesman, Terry Williams, said.

Men wearing green and orange safety vests walked up and down the tracks in an early morning fog, while others snapped pictures and climbed inside the wrecked shell of the front passenger car.

Mr. Williams said he couldn’t confirm reports that the engineer was text messaging shortly before the crash, but said investigators would consider that.

“We’re going to look into that, anything that can help us find the cause of this accident,” he said.

Rescue crews recovered two data recorders yesterday 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.

Investigators also will test the signals on the track and the brakes on the trains as well as interview Metrolink dispatchers.

Families of victims struggled with their loss after the coroner’s office released a partial list of the names of the dead. Among them was a Los Angeles police officer and an unidentified city employee who was believed to work in the general services office, Mayor Antonio Villaraigosa said.

There were no new reports of fatalities from hospitals today and the scene was cleared of bodies, Lieutenant Cheryl MacWillie of the county coroner’s office said.

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 (150-meter-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, Ms. Tyrrell said.

“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,” Ms. 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.”

Ms. Tyrrell said Metrolink made its determination from a review of dispatch records and computers.

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, which had a crew of three. The impact rammed the Metrolink engine backward, jamming it deep into the first passenger car.

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.

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