Seven people, including British tech tycoon Mike Lynch and his daughter, died when the ship went down in a sudden storm.

Prosecutors in Italy are investigating the captain of the superyacht that sank during a storm off Sicily last week, killing seven people, on possible charges including manslaughter, his lawyer said.

James Cutfield, a 51-year-old New Zealander, was being investigated for possible manslaughter and shipwreck, lawyer Aldo Mordiglia said on Monday.

Cutfield was one of 15 people on board the 56-meter (184 ft) Bayesian, which sank on August 19 after it was hit by a predawn storm while at anchor off Porticello, near Palermo.

British tech tycoon Mike Lynch, his 18-year-old daughter Hannah and five others were killed.

Mordiglia, one of two lawyers appointed for the captain’s defence, said Cutfield would be questioned by prosecutors on Tuesday. He was previously questioned in the aftermath of the incident, while other crew members were questioned on Monday.

Under Italian law, being under investigation does not imply guilt and does not mean formal charges will follow. Under maritime law, a captain has full responsibility for the ship, crew, and all on board.

On Saturday, the chief prosecutor, Ambrogio Cartosio, confirmed that an investigation had been launched.

He said his team would consider each possible element of responsibility including those of the captain, the crew, individuals in charge of supervision and the yacht’s manufacturer, Italian shipyard Perini Navi.

Investigators are focusing on how a boat deemed “unsinkable” by its manufacturer sank while a nearby yacht remained largely unscathed.

Prosecutors said the event was “extremely rapid” and could have been a “downburst” – a localised, powerful wind that descends from a thunderstorm and spreads out rapidly on hitting the ground.

They have said the investigation is likely to take time and will require the wreck to be salvaged from the sea. The Bayesian is currently lying on its right side, at a depth of about 50 metres (54.68 yards).

Lynch, 59, had invited friends and family for a holiday on the Bayesian to celebrate his recent acquittal on $11bn fraud charges linked to the sale of his software firm Autonomy to Hewlett-Packard.

The other five victims were Christopher Morvillo, one of Lynch’s American 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.