An Indian railway official says the derailment that killed 275 people and injured hundreds more was caused by an error in the electronic signaling system that led a train to wrongly change tracks and crash into a freight train. Authorities worked to clear the mangled wreckage of the two passenger trains that derailed Friday night in Odisha state in one of the country’s deadliest rail disasters in decades. The railway official says the root cause of the crash was related to an error in the electronic signaling system. She said a detailed investigation will reveal whether the error was human or technical. Despite efforts to improve safety, several hundred accidents occur every year on India’s railways, the largest under one management in the world.