A manslaughter investigation has been opened into the deaths of seven people in the sinking of a luxury yacht off the coast of Sicily, an Italian prosecutor said.

British tech mogul Mike Lynch and his 18-year-old daughter Hannah were among six people recovered after the Bayesian superyacht sank near Porticello at about 5am local time on Monday.

The body of Canadian-Antiguan national Recaldo Thomas, who was working as a chef on the superyacht, was recovered at the scene on Monday.

Ambrogio Cartosio, public prosecutor of nearby town Termini Imerese, said in a press conference at the town’s court on Saturday that his office has opened an initial investigation into manslaughter and negligent shipwreck, according to a translation.

He added that they are conducting an investigation against unknown persons.

Mr Cartosio said he thought it probable that offences were committed but insisted investigators needed time to establish the facts.

Morgan Stanley International bank chairman Jonathan Bloomer, his wife Judy Bloomer, Clifford Chance lawyer Chris Morvillo and his wife Neda Morvillo were also recovered from the wreckage.

The press conference heard that no post-mortem examinations have been carried out yet.

Prosecutors were questioned about the captain of the Bayesian and its crew.

Asked whether the crew will remain in Sicily, Mr Cartosio said: “There’s no obligation but they should be available for the investigation.”

The press conference heard authorities still have questions to ask the captain but that they cannot keep people in the country under Italian law.

The prosecutor in charge of the case, Raffaele Cammarano, was asked about the crew undergoing alcohol and drug testing, and said officials were trying to conduct those tests.

He was asked how it is possible that most of the crew managed to survive and said the incident happened suddenly and the inquiry will look into it.

Mr Cammarano suggested that passengers may not have been able to escape from the yacht because they were asleep.

Asked why they were not woken up or alerted, he said that is something investigators are trying to work out.

He said several of the bodies onboard the sunken yacht were found in a single cabin which was not theirs.

Maritime director of western Sicily Rear Admiral Raffaele Macauda said the weather at the time of the yacht’s sinking was abnormal and there was nothing to suggest such an extreme situation would arise.

He told the press conference that there was no tornado alert.

Mr Cammarano added that the yacht had been hit by a downburst, which are powerful winds that descend from a thunderstorm and spread out quickly once they hit the ground.

Officials said they would be looking at how it could affect one vehicle and not other nearby vessels.

Mr Macauda could not confirm how long it would take to retrieve the shipwreck of the sunken yacht and made clear that the owners will bear the full cost of retrieval, although he could not estimate the figure.

The bodies of all six missing passengers were taken to shore in the small fishing village of Porticello, about 11 miles from the Sicilian capital Palermo.

Tributes were paid to those who died, with Hannah’s sister calling her “the most amazing, supportive and joyful sister and best friend to me”.

Of the 22 passengers and crew on board, 15, including Mr Lynch’s wife, Angela Bacares, were rescued after escaping on to a lifeboat.

The boat trip was a celebration of Mr Lynch’s acquittal in a fraud case in the US.

The businessman, who founded software giant Autonomy in 1996, was cleared in June of carrying out a massive fraud relating to its 11 billion dollar (£8.64 billion) sale to US company Hewlett Packard.