Federal officials in the U.S. say a locked track switch is the most likely cause for the collision of a passenger train with a freight train on Sunday. Two people died and more than a hundred were injured in the accident in South Carolina.
"The position that we found it (the switch) in yesterday was locked in a position that it would be lined to go into the siding. It literally had a padlock on it locking it into that position," said the Chairman of the National Transportation Safety Board, Robert Sumwalt.
The fact that the switch is probable cause has raised questions about delays to a system being rolled out to prevent such crashes.
Officials said the railway signaling system was down so crews could install a "positive train control" system, which uses sensors and GPS to prevent trains from colliding or derailing.