An explosion ripped through two cars of a passenger train in eastern India on Monday, killing four people and injuring at least 50 others, police said. The cause of the blast was not immediately known. It was not clear if any explosive device had been planted in the train or on the track. The explosion occurred near Belacoba train station, about 550 kilometers (345 miles) north of Calcutta, the capital of West Bengal state, said the state's Home Secretary Prasad Ranjan Roy. Officials did not name any suspect, and no one immediately claimed responsibility.