DES MOINES (AP) — A misaligned switch leading into a rail yard caused a freight train to slam into some empty train cars in Bettendorf, killing the conductor and engineer, the National Transportation Safety Board said Wednesday.

The collision happened about 2 a.m. on July 14, 2009, when a Dakota, Minnesota & Eastern freight train went into the rail yard instead of staying on the main track. It hit 19 Burlington Northern Santa Fe cars that were parked in the rail yard.

The NTSB said in a report that the hand-operated switch had been “left incorrectly lined” from the main track onto the yard track by the BNSF crew, which had entered the rail yard about two hours earlier. Workers then failed to catch the mistake.