Investigators with the National Transportation Safety Board (NTSB) say a freight train involved in Tuesday's fatal accident outside of Los Angeles may have failed to heed a red warning light before colliding with a commuter train. NTSB chairwoman Marion Blakey told reporters Wednesday that investigators had ruled out the possibility that faulty signal lights or malfunctioning brakes led to the collision.

Blakey said officials involved in the investigation were interviewing crewmembers of the Burlington Northern Santa Fe train to determine why it did not stop at the red signal light. According to initial reports, the freight train passed the red signal moving at 48 mph. It began braking about 2,100 feet before the crash, slowing to 20 mph before slamming into the Metrolink commuter train. The Metrolink engineer, who ordered the commuter train to stop after noticing the freight train coming, warned several passengers in the first car before the collision. Two people were killed and hundreds more were injured in the crash.