PLACENTIA, Calif. -- Investigators trying to determine why a freight train plowed into a passenger train have turned their attention to the moments before the deadly crash, when they say the freight train ran a red light, according to a wire service.

“There is no question the Burlington Northern train should have stopped,” National Transportation Safety Board Chairwoman Marion Blakey said Wednesday. “The question is why it didn't stop.”

Two people were killed and more than 260 others were injured Tuesday when the Burlington Northern Santa Fe freight train crashed into a Metrolink commuter train during the morning rush hour.

Investigators found no problems with railroad signals, equipment or the tracks, Blakey said, adding other possible causes, including human error, were still being evaluated.

In the moments before the accident, Blakey said, the Burlington Northern freight passed a yellow light, but did not slow to 30 mph in preparation for an upcoming red light.

“That was the procedure called for at this junction,” she said.

When it reached the red light, the train was moving at 48 mph.

The freight train's brakes were not applied until after it passed the red light, Blakey said. It braked for 1,739 feet, slowing to 20 mph by the time it hit the stopped Metrolink train and shoved it 334 feet down the track.

The impact shattered windows, buckled one of the commuter train's three passenger cars and sent riders flying in all directions. Rescue workers took 162 people to hospitals.

The Metrolink engineer, who saw the freight train coming, brought his train to a halt and began to run through the train warning passengers.

“He acted very quickly and from what we can tell, he did everything correctly,” Blakey said.

Investigators were interviewing crew members of both trains and pulling personnel records and work schedules. Tests for alcohol had come back negative, with the results of drug tests expected by the end of the week, Blakey said,

“We want to look particularly at that 72-hour window before the crews came on duty to see what may have factored in in terms of their performance,” she said.

Burlington Northern Santa Fe spokesman Richard Russack withheld comment on the NTSB's preliminary findings.

“We have participated fully with the NTSB in the investigation so far and we will continue to participate and we will wait until the final report is produced before we make any further comment,” Russack said.

It was the worst accident in the nine-year history of Metrolink, which carries 32,000 passengers daily on 128 trains.

Killed in the accident were Robert Kube, 59, of Moreno Valley, and Lawrence I. Sorensen, 48, of Riverside. Both men died of internal injuries from blunt force trauma, Orange County sheriff's spokesman Jim Amormino said Wednesday.

NTSB investigators retrieved the event recorders that provide mechanical data on the trains, such as speed, braking maneuvers and use of the horn. Recorded radio conversations between the dispatcher and the crews will also be analyzed, Blakey said.

The freight train was en route from Los Angeles to Clovis, N.M., hauling 67 loaded container cars. The train company owns and maintains the stretch of rail where the crash occurred.

The Metrolink train was traveling from Riverside to San Juan Capistrano.