Prosecutors in Italy said Saturday they have opened an investigation into culpable shipwreck and multiple manslaughter after a superyacht capsized during a storm off the coast of Sicily early Monday, killing seven people on board. They included British tech magnate Mike Lynch and his daughter, and the ship's Canadian chef. 

Termini Imerese prosecutor Ambrogio Cartosio confirmed the investigation has been launched, but said no suspect is currently identified. 

"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. 

Cartosio said his team will carefully consider each possible element of responsibility, including those of the ship's captain, the crew, individuals in charge of supervision, the ship-builder and others.

"For me, it is probable that offences were committed, that it could be a case of manslaughter, but we can only establish that if you give us the time to investigate," he said.

The main question investigators are focusing on is how the Bayesian — a boat deemed "unsinkable" by its manufacturer, Italian shipyard Perini Navi — sank while a nearby sailboat remained largely unscathed.

WATCH | What we know about the yacht's sinking:

How the Bayesian superyacht sank in minutes | About That

An investigation is underway to determine why a superyacht sank off the coast of Sicily, killing seven on board. Lauren Bird breaks down expert analysis about the speed at which it sank and explores whether more could have been done to prevent it.

Prosecutors said the event was "extremely rapid" and information they gained seemed to point to a "downburst," a localized, powerful wind that descends from a thunderstorm and spreads out rapidly upon hitting the ground.

Initially, civil protection officials said they believed the yacht, which featured a distinctive 75-metre aluminum mast, was struck by a tornado over the water, known as a waterspout. 

Investigators were also asked why the crew was almost entirely saved, except for the chef, while six passengers remained trapped in the hull. 

Local officials confirmed that most of the bodies recovered were found in the same part of the ship — on the left side and closer to the surface — suggesting that passengers had sought safety in the cabins where the last air bubbles had formed.

Deputy prosecutor Raffaele Cammarano said it was likely that the passengers were asleep, adding that one main focus of the investigation will be to ascertain whether they were alerted by someone. 

Cammarano confirmed that one person was on watch in the cockpit. 

Rescuers on Friday brought ashore the last of seven bodies from the Bayesian, a 56-metre British-flagged luxury yacht. The sailboat was carrying a crew of 10 people and 12 passengers.

The seventh victim was Hannah Lynch, 18, the daughter of Mike Lynch, whose body was recovered 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.

Rescuers struggled for four days to find all the bodies, making slow headway through the interior of the wreck lying on the seabed 50 metres below the surface. 

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