A Polish historian on Friday claimed he had found the Amber Room, a long-lost Russian treasure looted by the Nazis during the Second World War.
Bartlomiej Plebanczyk said he believed he had located the missing artwork in a German wartime bunker in north-eastern Poland.
Radar tests showed there was a secret chamber at the back of the bunker where the treasure could be hidden, he said.
The claim comes after two treasure-hunters said they had discovered a Nazi gold train hidden in Poland last year — only for an extensive search to find no trace of it.
The Amber Room was an 18th century chamber decorated entirely with panels of amber and gold that was regarded as an “eighth wonder of the world”.
It was seized by Nazi troops during the war and taken to the then German city of Königsberg, in what is today the Russian enclave of Kaliningrad.
It disappeared after the war. An official Soviet investigation found that it was almost certainly destroyed either in RAF bombing or by Russian shelling.
But rumours that it somehow survived have persisted and it has long been sought by treasure-hunters.
Mr Plebanczyk says he is “almost certain” he has found it.
The bunker where he claims it lies is in the woods near Mamerki, a small Polish village some 60 miles from the city of Kaliningrad.
The historian, who is head of the Mamerki Museum, said a local resident had described seeing German trucks bringing heavy cases to the bunker at the end of the war.
Other residents claimed to have seen Erich Koch, a notorious Nazi war criminal who was a senior official in Königsberg at the time of the Amber Room’s disappearance, brought to the site from a Polish prison in the 1960s.
Authorities in the nearest town of Wegorzewo said they would investigate the contents of the hidden chamber.
“If it’s not the Amber Room, then maybe it’s some other treasure,” Andrzej Lachowicz, the deputy mayor, told local television.
Last year two treasure-hunters claimed they had located a long-fabled train of Nazi gold believed to have gone missing at the end of the war in a complex of underground tunnels near the city of Wałbrzych.
At one point, there was even a claim the train might contain the Amber Room.
But an extensive survey of the tunnels by Polish scientists found no trace of the train.