The Thursday explosion in the Maersk Tokyo vessel, now moored 43 nautical miles northwest off Jebel Ali port near here in international waters, might have been caused by welding work aboard, Lt Col Abdul Jalil Mahdi, acting head of Dubai Police Ports and Airports Security, was quoted as saying by the daily.

The four Indians, whose names were not disclosed, were last seen at a store on the left part of the ship where the explosion occurred, Mahdi said.

``We are not sure whether they are still on the ship or jumped off. I myself surveyed the area but there is no trace,'' he said. ``May be they are trapped in the store.''

The fire caused by the explosion was put out on Saturday but smoke is still coming out of it, Mahdi said, adding it was not being towed to a port for the fear that itmight explode.