NHK has learned that a Maritime Self-Defense Force destroyer probably veered off course and struck submerged rocks before becoming stranded in waters off the western Japanese prefecture of Yamaguchi.
On Tuesday, the MSDF destroyer Inazuma lost the ability to navigate under its own power near an island in the Seto Inland Sea. Part of a blade from one of the ship's two propellers had broken off and there are cracks and dents on the ship's bow.
Sources close to the investigation say Japan Coast Guard divers on Friday found traces of coating film believed to be from the vessel on rocks in nearby shallows with some of the rocks cracked.
The shallows are several meters deep and are located over 200 meters from a beacon installed to alert vessels to underwater obstacles.
The sources say GPS data shows the destroyer was sailing in the area at the time of the incident.
The Coast Guard is analyzing the coating film that was found on the rocks as well as investigating whether the traffic safety law was violated.
The Inazuma remains stranded and the Maritime Self-Defense Force says it is unclear when the vessel will be towed back to port.