Five bodies have been found in the search for six missing people after a luxury yacht sank in a tornado off the Sicilian coast, the head of Sicily’s civil protection agency Salvatore Cocina said.

It comes after the body of man believed to be the boat’s chef, Recaldo Thomas, a Canadian-Antiguan man, was recovered near the yacht on Monday.

Among those missing are British tech magnate Mike Lynch after the Bayesian sank at around 5am local time on Monday when it was moored half a mile off the coast of Porticello.

The cruise was reportedly a celebration of Mr Lynch’s recent acquittal on fraud charges in the US.

– Who is involved and why were they there?

Mr Lynch and his 18-year-old daughter Hannah – who had recently finished her A-levels and was bound for Oxford University – remain missing.

Also unaccounted for are Jonathan Bloomer, chairman of Morgan Stanley and insurance company Hiscox, and his wife Judy, a psychotherapist; and Chris Morvillo, a lawyer from Clifford Chance and part of the legal team representing Mr Lynch, and his wife Neda, who reportedly runs a luxury jewellery line.

The body of a man believed to be chef Recaldo Thomas, a Canadian-Antiguan man working onboard, was recovered near the yacht.

Fifteen of the 22 people onboard – including Mr Lynch’s wife, Angela Bacares – were rescued after escaping on to a lifeboat.

The Telegraph reported Mr Lynch had guests from the legal firm that represented him and his own company to join him on the voyage.

Among others rescued were Charlotte Golunkski and her one-year-old daughter Sophie. Ms Golunkski kept her daughter alive by holding the girl over her head in the water.

– How did the boat sink?

Italian authorities said stormy conditions caused the yacht to sink, but investigations are continuing.

It is believed the luxury vessel may have been hit by a water spout, a rotating column of wind that forms over a body of water and is often likened to a tornado.

According to the US National Ocean Service, tornadic weather spouts have the “same characteristics” as a land tornado and are often accompanied by severe thunderstorms, high winds and seas, large hail and frequent dangerous lightning.

– What search and rescue efforts are under way?

Salvatore Cocina, the head of Sicily’s civil protection agency, told the PA news agency that four bodies have been recovered and that efforts to bring a fifth to shore are “ongoing.”

In the afternoon, body bags were seen being taken to the port of Porticello, where dozens of emergency services staff were waiting.

Vincenzo Zagarola of the Italian coastguard previously said the missing tourists were all feared dead.

Asked about the likelihood of them being alive, he said: “Never say never, but reasonably the answer should be not.”

Italy’s fire brigade said it developed a plan to enter the wreckage of the Bayesian, which is resting on the seabed off the coast at a depth of 50 metres. It described the operation as “complex”, with divers limited to 12-minute underwater shifts.

Remotely controlled underwater vehicles are being used, with naval units and cave divers also taking part in the search, the Italian Coastguard has said.

Divers reached parts of the vessel through the gap, the Giornale Di Sicilia reported on Tuesday.

“If you manage to get inside, you understand there is a world of objects. So, getting inside and descending into the compartment below from the stairs that are narrow and going into all of the cabins is a really hard and difficult job,” fire department diver Marco Tilotta told the Reuters news agency, according to the BBC.

“We are not stopping. We have resources, manpower and means. Our goal is to find all the people who are missing, so that is our job.”

Dr Jean-Baptiste Souppez, a senior lecturer of mechanical, biomedical and design engineering at Aston University, said the next 24 hours are “crucial” to find survivors trapped inside the wreck.

“The speed at which the vessel sank (a few minutes, according to survivor and witness accounts) and the fact that it remains intact and on its side could favour the formation of small air pockets inside,” he said.

“This is obviously highly speculative and impossible to predict accurately.”

– Who is Mike Lynch?

The British multimillionaire, from Suffolk, owes his fortune to software firm Autonomy, which he sold to Hewlett-Packard for billions in 2011.

He graduated with a PhD from the University of Cambridge. He is married to Angela Bacares and they have two daughters.

He has a reported net worth valued at around £852 million, according to The Independent.

His business ventures led him to once being dubbed “Britain’s Bill Gates”, but also landed him in legal trouble.

Autonomy’s sale was dogged by fraud claims, and he faced civil action in the UK before being extradited to the US to face criminal charges.

In June, he was cleared of 15 fraud charges after allegations that he inflated Autonomy’s worth.

– What do we know about the Bayesian?

The 56-metre sailing boat was launched by Italian shipbuilder Perini Navi in 2008, according to the company website.

It was once called the Salute, but was later renamed after Mr Lynch’s PhD thesis on statistical theory by mathematician Thomas Bayes.

Media reports suggest the yacht’s owner is listed as Revtom Ltd, a company owned by Mr Lynch’s wife.

– Who was Stephen Chamberlain and how is he connected to the incident?

Mr Chamberlain was an associate of Mr Lynch and stood trial for fraud alongside him after Autonomy’s sale.

Days before the yacht disaster, Mr Chamberlain died after being hit by a car while out jogging.

Mr Chamberlain, Autonomy’s former vice president of finance, was cleared of all charges by a San Francisco court in June.

Relatives said in a tribute released through police that he was a “much-loved husband, father, son, brother and friend”.

“He was an amazing individual whose only goal in life was to help others in any way possible,” they said.