A group of Polish divers say they have discovered a World War II-era German ship with crates of contents that could be connected to the missing Amber Room from the Catherine Palace near St Petersburg.

The fabled amber and gold-leaf encrusted room, gifted to Peter the Great of Russia in 1716, was dismantled by the Nazis and taken to Königsberg, a Baltic port city in Germany that is now a Russian enclave. Some experts believe the Amber Room was destroyed by allied bombing raids on Königsberg.

The divers point out that after leaving Königsberg in 1945, the Karlsruhe steamer was sunk off the coast of Poland by Soviet warplanes with over 1,000 people on board and heavy cargo — with some contents not yet revealed.

“We have been looking for the wreckage since last year when we realized there could be the most interesting, undiscovered story lying at the bottom of the Baltic Sea,” Tomasz Stachura, one of the divers from the Baltictech group, said in a statement.

“It is practically intact. In its holds we discovered military vehicles, porcelain and many crates with contents still unknown.”

A replica of the Amber Room has been constructed in the Catherine Palace.