No Mechanical Failures Found at Rail Crash Site : Accident: Investigators focus on why the westbound train failed to stop. The head-on Corona collision left four dead and two injured.

Finding no evidence of a mechanical malfunction, federal investigators on Saturday concluded their on-site examination of last week’s train wreck that killed four and injured two others.

“The locomotives and the (railway) equipment worked as designed,” said Michael J. Martino, the National Transportation Safety Board’s investigator in charge.

Martino said in an interview that the investigation will shift to an analytical phase that could last months, as experts try to determine precisely what caused two freight trains to collide and explode in fire at 4:10 a.m. last Wednesday.

Officials have concluded that impact occurred after a westbound freight failed to stop on a sidetrack and then re-entered the central track, veering into an east-bound train that had the right of way.

All three crew members of the westbound train, traveling from Barstow to Los Angeles, died. The brakeman of the eastbound freight, bound from Los Angeles for Chicago, also was killed.

Martino and other investigators said the main, unanswered question is why the westbound freight failed to stop within the 8,370-foot sidetrack.

Tests of the locomotives, the rail tracks and the elevated signals that warn railway workers of oncoming trains have indicated that all the equipment functioned properly--raising the possibility that the westbound’s failure to stop may be attributable to human error.

“I’m sure (the on-site findings) will help to narrow the possibilities” of what caused the accident, said M. E. Curtis, an assistant superintendent for operations of the Atchison, Topeka & Santa Fe Railway Co.

Killed in the accident were Virginia C. Hartzell, 29, of Baldwin Park; Gary R. Ledoux, 35, of Highland, Calif.; James S. Wakefield, 55, of Fontana, and Ronald E. Westervelt, 51, of San Bernardino.

Martino said that the last radio communication from the westbound crew to Santa Fe dispatchers occurred when the train was “a little over one mile” east of where the crash would occur in Corona. Martino said the conversation gave no indication of trouble.

With all the westbound crew dead, Martino said investigators must rely on an encased cassette tape, called an event recorder, to discern how and when the freight’s brakes were applied and at what setting its throttle stood. He said the tape would be analyzed later this week in Washington, D.C.

As of Saturday, investigators had interviewed one of the two crash survivors, Warren Sanders, the conductor of the eastbound freight. According to Martino, Sanders said his train was traveling with a green signal light, consistent with investigators’ belief that the eastbound train had the right-of-way to the central track.

As Santa Fe began restoring freight traffic along the track affected by the crash, workers replaced 150 feet of an underground crude-oil pipe. Martino said the pipe was being replaced “strictly as a precaution,” adding that tests have confirmed that an adjacent underground natural gas line also was unscathed.