Indonesia's Java Sea is a gold mine for World War Two shipwrecks, meaning it’s also a haven for scrap metal scavengers. Now there are grim reports that metal scavengers are illegally dumping the bodies of soldiers and sailors in mass underwater graves.

Thousands of Dutch, British, US, Australian, and Japanese sailors died during the Battle of the Java Sea in 1942, one of the most important naval battles of the Pacific campaign. For the Allies, it was also one of the most devastating defeats at sea during WW2. Three Dutch boats – HNLMS De Ruyter, Java, and Kortenaer – and three British boats – the HMS Exeter, Encounter, and Electra – were among the ships that sunk beneath the waves during this battle.

In 2016, Dutch divers headed to the Java Sea with the plan of placing commemorative plaques on the shipwrecks, but they were nowhere to be found. It turned out these ships were among the dozens of wrecks that had been dismantled and sold off by illegal organized rackets of salvaging thieves. Teams of scavengers head out to track down the shipwrecks. Divers are then sent down and place explosives within the wrecks. The metal is then collecting and sold off to shady “under the counter” traders across Southeast Asia.

A contractor for one of the scavenging rings recently told Indonesian news site Tirto.id that they have regularly come across human skulls, hips, hand bones, and ribs during their work. After these remains are collected, they are either dumped back in the sea or put in sacks and buried in shallow graves near the harbors.

Understandably, since these remains almost undoubtedly belong to lost soldiers, the authorities are not too happy with these reports.

“There is new information that has reached us through the media. We must determine whether it is correct. We hope to do that quickly, because it is a very bad thing for the relatives of the war heroes who died in the Java Sea,” Halbe Zijlstra, the Dutch Minister of Foreign Affairs, told De Telegraaf.

The UK Ministry of Defense issued a similar statement to the Guardian. “Desecration of wrecks of war and merchant vessels causes distress to loved ones of those lost on board and is against international law. A military wreck should remain undisturbed and those who lost their lives onboard should be allowed to rest in peace,” it said.

The UK and Dutch governments are now looking into using a naval presence and technology to deter further grave robberies.