Enforcement officers found 100 unexploded artillery shells and rusted piles of metal on board the dredger in South China Sea.

The Fuzhou-registered Chuan Hong 68 was detained off the coast of the Malaysian state of Johor on May 28, the Malaysian Maritime Enforcement Agency said in a statement on Facebook on Tuesday.

In a joint operation with police, officers found 100 unexploded artillery shells on board.

Photos released by the agency showed piles of rusted metal on the boat’s deck as well as cranes and cutting equipment.

“Maritime Malaysia (Malaysian Maritime Enforcement Agency) does not rule out the possibility that this vessel is involved in the theft of old British warship wrecks,” the statement said.

The HMS Repulse and HMS Prince of Wales sank in the South China Sea after being attacked by Japanese fighter aircraft in December 1941. Nearly 850 sailors were killed in one of the worst disasters in British naval history.

The wrecks are designated war graves and are not supposed to be disturbed.

“We are distressed and concerned at the apparent vandalism for personal profit,” Dominic Tweddle, the director general of the National Museum of the Royal Navy, said in a statement after Malaysian media – tipped off by local fishermen – reported suspicious activity around the wrecks.

The Chuan Hong was initially detained for anchoring without a permit.

Its crew of 32, including 21 Chinese nationals, 10 Bangladeshis and a Malaysian, were being questioned, officials said.

In Beijing, Chinese Foreign Ministry spokesperson Mao Ning told reporters that the government was aware of the case.

The Chinese Embassy in Kuala Lumpur was in touch with the Malaysian authorities and had asked them to “handle the case justly in accordance with law”, she said, adding that Chinese citizens’ “security and lawful rights and interests” must also be protected.

The two British shipwrecks have been targeted previously by illegal salvage teams.