TOKYO, May 29 -- A fuel tanker exploded in waters off Hyogo Prefecture, western Japan at about 9:20 a.m. local time ( 0020 GMT) on Thursday, leaving the captain missing and four crew members badly injured, the Japan Coast Guard said.

There were eight crew members on board, seven of them have been rescued, a local fire department said. The missing captain is 64- year-old Masaichi Ando.

According to a Coast Guard official, the 988-ton vessel was anchored about two kilometers south of the Himeji Port, which lies 450 kilometers west of Tokyo. It had already unloaded heavy fuel oil at a port, but black smoke was seen billowing from the ship, up to 100-meter high.