Spain formally laid claim Thursday to a shipwreck that yielded a $500 million treasure, saying it has proof the vessel was Spanish.

Officials demanded the return of the booty recovered last year by a U.S. deep-sea exploration firm, saying the 19th-century shipwreck at the heart of the dispute is the Nuestra Senora de las Mercedes — a Spanish warship sunk by the British navy southwest of Portugal in 1804 with more than 200 people on board.

Tampa, Fla.-based Odyssey Marine Exploration had announced in May 2007 that it had discovered the wreck in the Atlantic — and its cargo of 500,000 silver coins and other artifacts worth an estimated $500 million.

At the time, Odyssey said it did not know which ship it was, and flew the treasures back to Tampa without Spain's knowledge, from an airport on the British colony of Gibraltar on Spain's southwestern tip.

The Spanish government filed evidence in a Tampa federal court to support its claim.

"We are talking about the remains of a Spanish navy vessel and the human remains of Spanish naval servicemen who died on board which have been illegally disturbed," Culture Ministry Director General Jose Jimenez said.

"It is the property of the Spanish navy, government and people, and we want it all back," said Adm. Teodoro de Leste Contreras, who runs a naval museum owned by the ministry.

Washington-based lawyer James Goold, representing the Spanish government in the case, said U.S. Judge Mark Pizzo will convene the two parties to review the case before deciding who gets to keep the treasure.

Goold said at a Madrid news conference that he expected Odyssey would keep "not a penny" of the salvage.

Spain argues that the entire treasure should be returned because naval vessels remain the property of the nation that flagged them, regardless of where they lie, under the principle of sovereign immunity.

Goold said Spain's evidence — based on material provided by Odyssey under court order — proved the ship and cargo definitely were Spanish property.

"Spain has not abandoned or otherwise relinquished in any way its ownership of Mercedes," Spain's petition said.

Odyssey said it would issue a statement after reviewing Spain's claim. But company officials have said in the past that they believe the court will award them most of the treasure.

Naval and coin experts say they have proof that the treasure, now held in a warehouse in Tampa, came from the Nuestra Senora de las Mercedes. The coins included gold doubloons, or "pieces of eight," minted in 1803 in Lima, Peru, bearing the image of Spain's King Carlos IV, ministry coin expert Carmen Marcos said.

The Mercedes exploded and sank in a naval battle as it sailed back to Spain from South America.

Spain's claim said artifacts on the seabed, their distribution and other characteristics, as well as artifacts taken by Odyssey, "further identify the site as the remains of Mercedes."

Odyssey also said the ship was probably the Mercedes after Pizzo last month forced the company to disclose information on the salvage, including the identity of the ship and its location.