Mumbai, March 7 : An explosion followed by a massive fire ripped through a Singapore-flagged container ship with 13 Indian crew including the captain off Agatti Islands, the Coast Guard said on Wednesday. Four crewmen, including an Indian, are reported missing. Casualties are feared in the disaster that struck on the high seas around 9.45 p.m. on Tuesday. The cause of the incident, which occurred off the south-west coast of India, is not yet known, the official said.