Prosecutors in Italy said Saturday they have opened an investigation into shipwreck and manslaughter after a superyacht capsized during a storm off the coast of Sicily, killing seven people onboard.

Termini Imerese prosecutor Ambrogio Cartosio confirmed the investigation but said no suspect is currently identified. Investigators are hoping to salvage the ship, which is lying on the seabed 164 feet underwater, but that may take months. 

“We are only in the initial phase of the investigation. We can’t exclude any sort of development at present,” he told reporters at a news conference. 

The main question investigators are focusing on is how a sailing vessel deemed “unsinkable” by its manufacturer, Italian shipyard Perini Navi, sank while a nearby sailboat remained largely unscathed.

Civil protection officials said they believe the yacht, which featured a distinctive 246-feet aluminum mast, was struck by a tornado over the water, known as a waterspout, and sank quickly. 

Rescuers on Friday brought ashore the last of seven bodies from the sinking of The Bayesian, an 184-foot British-flagged luxury yacht that went down in a storm while docked near the small Sicilian village of Porticello early Monday. The sailboat was carrying a crew of 10 people and 12 passengers.

The body was believed to be that of Hannah Lynch, 18, the daughter of British tech magnate Mike Lynch. His body was recovered on Thursday. He had been celebrating his recent acquittal on fraud charges with his family and the people who had defended him at trial in the United States. His wife, Angela Bacares, was among the 15 survivors who escaped in a lifeboat. 

“The Lynch family is devastated, in shock and is being comforted and supported by family and friends. Their thoughts are with everyone affected by the tragedy,” a spokesperson for the family said in a statement issued Friday.

The other five victims are Christopher Morvillo, one of Lynch’s U.S. lawyers, and his wife, Neda; Jonathan Bloomer, chairman of Morgan Stanley’s London-based investment banking subsidiary, and his wife, Judy; and Recaldo Thomas, the yacht’s chef.

Rescuers struggled for four days to find all the bodies, making only slow headway through the interior of the wreck because of how far below the surface it is. Searchers used an underwater drone as part of the recovery efforts. 

Area resident Maria Vizzo told CBS News that the region has “never seen something like this.” 

“Sunday night here we saw the end of the world in Porticello,” Vizzo said in Italian. “The town of Porticello is mourning these people who died. Everyone is talking about it on the radio, and in the news. We are here. We pray to the Lord, and we ask for a blessing for those who died.”