Malaysia’s maritime agency said Tuesday a Chinese barge likely plundered two World War II British shipwrecks in the South China Sea after discovering 100 more old artillery shells on the detained vessel.

Malaysian media reported that illegal salvage operators are believed to have targeted the HMS Repulse and the HMS Prince of Wales, which were sunk in 1941 by Japanese torpedoes days after the attack on Pearl Harbor.

A total of 842 sailors perished, and the shipwrecks off the coast of Malaysia’s central Pahang state are designated war graves. Fishermen and divers alerted authorities after spotting a foreign vessel near the area last month.

The maritime agency detained the barge, registered in Fuzhou, China, on Sunday for anchoring without a permit off southern Johor state. Upon investigation, the agency found piles of scrap metal and an artillery shell believed to be from World War II on the vessel.