Claims that a team of explorers discovered a famous 17th Century pirate shipwreck off the coast of Madagascar have been dismissed by UN experts.
A 50kg (7st 9lb) bar of "silver treasure" recovered from the sea was in fact 95% lead, the UN statement said.
It was presented to Madagascar's president at a special ceremony in May.
The wreckage that the ingot was found in was not that of the ship captained by notorious Scottish pirate William Kidd, the UN investigators added.
A technical team from Unesco, the UN's cultural arm, was sent to investigate the find, which made global headlines.
"The mission showed that several historic wrecks lie indeed in the bays of Sainte-Marie island," the Unesco statement said.
"However, what had been identified as the Adventure Galley of the pirate Captain Kidd has been found by the experts... to be a broken part of the Sainte-Marie port constructions."
Authorities in Madagascar should "only permit interventions by a competent team led by a qualified underwater archaeologist", Michel L'Hour, head of the Unesco technical team, added.
Capt Kidd, who inspired Robert Louis Stevenson's book Treasure Island, was first appointed by the British authorities to tackle piracy but later became a ruthless criminal and was executed in 1701.
In May US explorer Barry Clifford said: "Captain's Kidd's treasure is the stuff of legends.
"People have been looking for it for 300 years. To literally have it hit me on the head - I thought what the heck just happened to me. I really didn't expect this."