A signal error caused the devastating train derailment in India that killed at least 275 people and injured hundreds more, officials said Sunday. Two passenger trains were involved in the deadly incident, which occurred Friday night. Authorities were still working to clear the wreckage Sunday evening. A senior Indian railway official told the Associated Press that one of the trains, a high-speed Coromandel Express, had been given a signal to run on an already-occupied line, which caused it to ram into a freight train carrying iron ore. After the collision, the passenger train fell onto another set of tracks, where it collided with another train carrying more than 2,000 people. “The system is 99.9% error free. But 0.1% chances are always there for an error,” Jaya Verma Sinha, the railway official, said during a press conference—adding later that sabotage was not out of the question. “Nothing is ruled out,” they said.