JAKARTA, Indonesia – Indonesia has offered to help investigate the disappearance of the wreckage of three Dutch warships that sank during World War II off Java island, Dutch Prime Minister Mark Rutte said Wednesday.

Rutte, who is on an official visit to Indonesia, said the two countries will work together to determine what happened to the ships that sank in a 1942 battle in the crystal blue Java Sea.

An international investigation found that the wrecks of two of the warships are completely gone, while another has lost most of its pieces.

Some investigators believe scavengers may have looted the wrecks to obtain scrap metal.

“We will work together to find clarity on what happened and we will co-ordinate in the future,” Rutte said at a news conference after meeting with President Joko “Jokowi” Widodo.

The ships, along with three British warships and a U.S. submarine, were sunk by Japanese forces during the Battle of the Java Sea.

Reports say the wreckage of the British heavy cruiser HMS Exeter and destroyer HMS Encounter have also been almost totally removed. Underwater scans showed that parts of the wreck of the destroyer HMS Electra had also been plundered.

Indonesian Foreign Ministry spokesman Armanatha Nassir confirmed the bilateral co-operation to investigate and protect the historic relics. He did not rule out possible arrangements with other concerned countries.