The derailment happened in the exact same spot where another train ran off the tracks three years ago. But, the transit agency has yet to figure out what caused the problem.
There are 104 miles of track in the BART system and now there have been two derailments in the exact same spot -- in Concord -- within three years. It appears, the same section of track is implicated, an interlocking device known as a frog but investigators are also looking at whether the wheel axle of the train car itself froze and that's what damaged the frog.
Over the weekend, BART spokesman Jim Allison said there's no clear evidence the frog, or the interlocking device is the culprit behind both accidents.
"There's nothing obvious that we've looked at, that we've seen, so far that would lead us to believe that a derailment would occur. So, it's going to take some investigation," said Allison.
Besides BART, the California Public Utilities Commission is investigating the accident. The process could take up to a month.