The remains of British tech entrepreneur Mike Lynch were found on Thursday aboard his family’s superyacht, which sank off the coast of Italy after being caught in a sudden severe storm, as reported by a senior Italian official.

After the recovery of four bodies from the wreckage on Wednesday, Lynch’s 18-year-old daughter, Hannah, is now the sole person missing, according to Massimo Mariani from Italy’s interior ministry. It’s believed that her body may have been carried out to sea, Mariani stated.

Divers may face delays in locating her body due to the difficulties associated with accessing the submerged vessel, which lies over 160 feet beneath the surface, explained Luca Cari from the fire brigade. The search is complicated by the challenging conditions around the wreck.

Lynch, aged 59, was renowned for co-founding Autonomy, the largest enterprise software firm in the UK, which was sold to Hewlett-Packard in 2011. He had invited friends aboard the yacht to celebrate his acquittal in June regarding fraud charges linked to the sale of Autonomy.

The yacht, named the Bayesian and measuring 184 feet in length, sank just before dawn on Monday off the coast of Porticello, near Palermo, where it was stationed when a powerful storm struck. Out of the 22 people on board, 15, including Lynch’s wife Angela Bacares, were rescued and some were taken to the hospital. The body of the yacht’s chef, Ricardo Thomas, was subsequently recovered near the wreck.

A comprehensive search operation is currently underway to locate the six individuals who are still unaccounted for, including Lynch and his daughter, as well as Judy and Jonathan Bloomer, who is the non-executive chair of Morgan Stanley International, along with Clifford Chance lawyer Chris Morvillo and his wife, Neda Morvillo.

Jonathan Bloomer had served as a character witness for Lynch during his recent fraud trial, while Chris Morvillo, an American national, was part of Lynch’s defense team.

Hannah, the younger of Lynch’s two daughters, remains the only one still missing following the discovery of the Bloomers and Morvillos on Wednesday. She was about to begin her studies in English literature at Oxford University, as reported by the Sunday Times.

An investigation has been initiated by local prosecutors to determine the cause of the incident.

The yacht, owned by Lynch’s wife, was constructed in 2008 by the Italian shipbuilding company Perini. It was built to adhere to international maritime safety standards and was commercially certified by the UK’s Maritime and Coastguard Agency, according to Matthew Schanck, chairman of the Maritime Search and Rescue Council.

Experts believe that a water spout, which is akin to a tornado over water and can reach speeds of 120 mph, along with the enormous weight of the yacht’s mast—one of the largest globally—may have played a role in the sinking.