Investigators examining the sinking of a luxury yacht off the coast of Sicily have outlined what they know six days on.

Seven people died when the Bayesian, a 56-metre sailing boat, sank to the bottom of the ocean during bad weather early on 19 August.

There were 22 passengers and crew on board, 15 of whom managed to escape onto a lifeboat.

In their first press conference about the tragedy, at a court in Termini Imerese, Sicily, on Saturday, Italian prosecutors confirmed that a manslaughter and negligent shipwreck investigation has begun over the disaster’s seven deaths.

Officials were unable to answer a number of queries from the media, saying they needed time to establish the facts, but they did shine a light on some previously unknown details.

A manslaughter investigation has been opened into the deaths of seven people in the sinking.

British tech businessman Mike Lynch and his 18-year-old daughter Hannah lost their lives, alongside Morgan Stanley International bank chairman Jonathan Bloomer, his wife Judy Bloomer, Clifford Chance lawyer Chris Morvillo and his wife Neda Morvillo, and Canadian-Antiguan national Recaldo Thomas, who was working as a chef on the yacht.

All of their bodies have now been recovered.

Chief prosecutor of Termini Imerese, Ambrogio Cartosio, said his office has opened an initial investigation into manslaughter and negligent shipwreck.

He told reporters they would ascertain whether the captain, crew, individuals in charge of supervision, the ship-builder, or others could bear responsibility.

He added: “We will establish each element’s responsibility – that will be done by the inquiry, so we can’t do that prematurely.

“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.

“Media timing is completely different from that of a prosecutor. We need a minimum amount of time to come to a proper scientific conclusion.”

The inquiry is currently an Italian investigation with local involvement, but Mr Cartosio said: “I cannot tell you with any certainty that the inquiry will be exclusively Italian.

“There will be developments, I’m sure, on that score.”

Witnesses described seeing a waterspout form during the storm before the sinking of the Bayesian yacht, which is similar to a tornado over a body of water.

However, deputy prosecutor Raffaele Cammarano told the press conference that “from the information we have, it is a downburst we are talking about”.

BBC Weather forecaster Ben Rich said a downburst occurs when air races downward from the base of a cloud. It produces a powerful gust of wind that blows unpredictably outwards in different directions.

He said it can be confused with tornadoes or waterspouts because the damage caused can be similar.

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 there was no tornado alert.

Officials said they would be looking at how a downburst could have affected the Bayesian and not other vessels nearby.

The body of Recaldo Thomas, who was working as a chef on the yacht, was found outside of the vessel and was the first to be discovered.

The bodies of the remaining six people were recovered from cabins on the left side of the yacht after it had sunk, the chief of the Palermo fire service said.

Girolamo Bentivoglio said that specialised divers attempting to retrieve the bodies had to deal with “very little visibility due to the weather conditions” and were called in from across the country as part of a search-and-rescue operation which involved “some 70 people” each day.

He added: “The yacht obviously pinned to the right and obviously the [people] tried to go on the other side and then took refuge in their cabins.

“We found four or five bodies in the cabin on the left and there was another one in the third cabin on the left too, and they were in the higher part of the wreck.”

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 precisely what we are trying to ascertain from the statements made during the interrogation of the survivors – an essential point in the inquiry, obviously.”

He said several of the bodies were found in a single cabin.

He said: “The bodies were found in a cabin which was not theirs, but this doesn’t give us any kind of certainty about what happened.

“We have no idea of the reasons for their all being found in the same cabin.”

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.

Mr Cammarano was asked about the crew undergoing alcohol and drug testing, and he said officials were trying to conduct those tests.

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

No information has yet been gleaned from an examination of the seven people who died, prosecutors said.

In response to a question about whether post-mortem examinations have been carried out, Mr Cammarano said: “There are a whole number of preliminary stages to go through before the autopsies.”