Greg Brooks of Maine, US, says the S.S. Port Nicholson was carrying a load of platinum bars now worth more than $3 billion. The platinum was a payment from the Soviet Union to the U.S. for war supplies and it is believed the vessel was also carrying gold bullion and diamonds.

If Brooks’s claim is true, it could be one of the richest sunken treasures ever discovered.

However, if it was laden with precious metals, who owns the hoard could become a matter of international dispute.

Brooks said the wreck was found sitting in 700 feet of water 50 miles offshore is that of the S.S. Port Nicholson, sunk in 1942.

He said he and his crew identified it via the hull number using an underwater camera. He now hopes to begin raising the treasure as soon as later this month.

“I’m going to get it, one way or another, even if I have to lift the ship out of the water,” Brooks said.

But Robert F. Marx, an underwater archaeologist, maritime historian and owner of Seven Seas Search and Salvage LLC in Florida said Brooks’s story should be viewed with scepticism.

Both an American company and an English company had gone after the contents of the ship years ago and Marx said they surely retrieved at least a portion.

“Every wreck that is lost is the richest wreck lost. Every wreck ever found is the biggest ever found. Every recovery is the biggest ever recovery,” Marx said.

In other big finds, treasure hunter Mel Fisher made international headlines in 1985 when he discovered a $450 million mother lode of precious metals and gemstones from a Spanish galleon that went down off Florida in 1622.

In another case, a Tampa exploration company has been ordered by the courts to return $500 million worth of treasure from a Spanish warship to Spain. The ship was sunk by the British navy during a battle off Portugal in 1804.