SEOUL, South Korea >> A South Korean cargo ship was rocked by an explosion off the country’s west coast Sunday, leaving five people dead and six others missing, officials said.

The unexplained explosion tore apart the front of the ship and left the 4,198-ton vessel half-submerged, coast guard officials said. Two of the five bodies had serious external wounds, suggesting they were killed by the explosion, coast guard officer Kim Dong-jin said.

Five crewmen were rescued and searchers were trying to locate the six missing, the coast guard said in a statement.

The explosion occurred relatively far from the tense sea border with North Korea, and the coast guard doesn’t suspect the North was involved, coast guard officer Ko Jae-young said.

North Korea was accused of torpedoing a South Korean warship in 2010, killing 46 sailors, though it has denied involvement.

The ship’s captain, who survived, said the explosion may have been caused by static electricity which ignited gasoline vapors from an onboard tank where 11 crew members were working before the blast, according to Yonhap news agency.

The cargo ship, which usually carried refined petroleum products and chemicals, was carrying 80 tons of Bunker-C oil and 40 tons of diesel oil for fuel when it exploded, the coast guard statement said. Oil leakage wasn’t immediately reported, it said.

Eleven members of the crew are from South Korea, and the other five are from Myanmar.