Spain's Civil Guard on Thursday seized a ship of a U.S. treasure hunting company, which was accused of stealing a treasure of coins from a Spanish shipwreck.
The ship, Ocean Alert, owned by the Florida-based Odyssey Marine Exploration company, was seized around 9 a.m. (0700 GMT), 5 km off the southeastern coast, the Civil Guard said in a statement.
The ship just left the British colony of Gibraltar on Spain's southern tip and entered Spanish waters, the statement added.
Ocean Alert was followed by a Civil Guard patrol boat for 5 km before it left Gibraltar waters and was forcefully boarded by four officers.
A Spanish judge issued a warrant on all of Odyssey's boats in June, after the company announced it had found 17 tons of gold and silver coins aboard a sunken ship in international waters off the Spanish coast.
In late June, Carmen Calvo, Spain's former culture minister, said that Odyssey had stolen a Spanish cargo that sank in the Atlantic Ocean during the colonial era, and that Spain would prosecute the company on charges of looting and illegal activities.
Cesar Antonio Molina, who took over from Calvo on June 6, vowed to defend Spain's heritage and said he had hired a team of U.S. lawyers to work on the case.
On May 19, Odyssey said it legally recovered gold and silver coins worth an estimated 500 million U.S. dollars from a colonial-era wreck code-named Black Swan at a location in the Atlantic Ocean which it refuses to disclose.
Meanwhile, British government sources said London would raise the case with the Spanish Foreign Ministry as the boat should not be detained in international waters without permission from Panama, where the boat is registered.
Spain ceded control of Gibraltar to Britain in 1713 but has since been seeking to regain the strategic territory that sits at the entrance to the Mediterranean.