Italian archaeologists fear that an American nuclear research submarine may be exploring sunken wrecks in Italy's territorial waters.
Their claims followed the sighting of a mysterious conning tower which emerged from the sea in front of thousands of holidaymakers off a Sicilian beach.
Some believe the tower belongs to NR-1 (Nuclear Research-1), a US navy submarine on loan to Robert Ballard, the deep sea explorer famous for having discovered the wrecks of the Titanic and the Bismark.
For several months Dr Ballard has been using the sub, which is only 15 metres long and is fitted with mechanical arms, floodlights, cameras and special sensors, to explore the Mediterranean seabed.
In a recent conference at the National Archaeological Society in Washington, he announced he had found a "graveyard" of ships between Sicily and Tunisia dating from the first century bc to ad 400. As proof, he displayed 115 amphorae and other archaeological objects.
According to Dr Ballard, the site is on an ancient trade route between Rome and Carthage and is in international waters. But in July, bathers on a beach in western Sicily were treated to the spectacle of a conning tower emerging from the sea just offshore - well within Italian territorial waters, and over an area which the Italian cultural heritage authorities know to contain a wreck of archaeological value.
Domenico Macaluso, one of Sicily's most eminent archaeologists, said he was sure the conning tower belonged to NR-1 and that Ballard was operating freely outside and inside territorial waters. Macaluso said Ballard was "taking advantage of the superior technology he has available to rake the seabed".
Under Italian law, archaeological finds in the sea are the property of the state. The removal of archeological relics from land or sea is considered a serious crime and is punishable by imprisonment.
The department of underwater archaeology of the culture ministry has mapped out hundreds of wrecks from Roman times around the Italian coast. Most are simply watched over by the coastguard until teams of underwater archaeologists get around to the time-consuming and expensive procedure of examining them.
Dr Ballard has denied taking more than a few artefacts from the "graveyard", which lies well beyond Italy's 12-mile territorial limit. After the sighting of the conning tower a coastguard patrol boat was summoned. But when it reached the spot there was no sign of the submarine.
The Sicilian cultural heritage department has made a formal protest to the European authorities in Brussels asking for immediate steps to be taken to protect archaeological treasures from indiscriminate plunder.