A TOP US dive team has launched an expedition off the Irish coast to unravel one of the greatest mysteries of World War I.
The team will dive off the Cork coast to conduct the biggest exploration of the wreck of the cruise liner Lusitania in almost two decades.
The expedition is being filmed for a documentary entitled The Dark Secret which will be broadcast next year.
The sinking of the RMS Lusitania in 1915 by the German submarine U-20 is largely credited with having pushed the United States into World War I.
But it has remained controversial amid claims the civilian liner was carrying munitions.
The Cunard liner was hit by a single torpedo fired from a U-boat while off the Cork coast on May 7 1915, but it has never been established why it sank so quickly after being hit.
US divers, assisted by experienced Irish divers, will now spend the next 10 days examining the wreck site.