Poland's Ministry of Maritime Affairs told Euronews it will seek clarification from French authorities after alleging its soldiers were seen illegally diving at the site of the WWII Wilhelm Gustloff wreckage.

A patrol plane saw French soldiers from FS Pegase minesweeper — in the area as part of a joint training operation with Polish marines — diving near the wreckage on June 5, reports RMF radio.

A body has since been recovered from the site.

The MV Wilhelm Gustloff was built in 1937 for the Nazi party as a cruise liner for German public servants and workers but it was requisitioned in 1939 as part of the war effort and reconverted into a hospital ship.

As the Soviet army advanced on East Prussia, preparations began for the mass evacuation of German troops and civilians under the codename Operation Hannibal. Between 8,000 to 10,000 soldiers and civilians are believed to have boarded the Wilhelm Gustloff before it departed from Gdansk at noon on January 30, 1945.

It sunk nine hours later after being hit by three torpedoes from a Soviet submarine. Fewer than 1,300 people survived the attack, making it the greatest maritime disaster in history.

The wreckage, located some 40 kms north of the coastal city of Łeba, has been considered a war grave since 1994. Under Polish law, diving is strictly prohibited within a 500-metre radius of the site with permission to enter the perimeter granted only by the Maritime Office in Gdynia in an effort to prevent treasure-hunters from plundering the site.

Contacted by the Polish authorities at the time, the French ship's commander reportedly said he had not been aware of the ban to enter the area.

The French soldiers also alerted the Polish authorities that they had seen a body inside the wreckage, which was found a day later by Polish divers.

Local media believe it to be the body of Robert Szlecht, who disappeared in July 2012 while on a diving trip with friends.

Euronews has reached out to French authorities for comment.

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