(AFP) - Divers searching for six people missing after a superyacht sank off Sicily, including UK tech tycoon Mike Lynch, on Wednesday pulled four bodies from the wreck and reportedly found a fifth.

The grim development, after three days of searches since the "Bayesian" went down early on Monday morning, brings the death toll to six -- with one person still missing.

There was no official identification of the bodies but Lynch and his 18-year-old daughter Hannah are among those missing since the yacht was scuppered in a storm off the Italian island.

The 56-metre (185 feet) British-flagged sailing boat had been anchored some 700 metres off Porticello, east of Palermo, when it was struck by a waterspout -- akin to a mini-tornado.

It sank within minutes.

Fifteen people were rescued, including Lynch's wife and a woman with a one-year-old baby. But the body of a man, believed to be the yacht's chef, was found several hours later.

Lynch and his daughter, his lawyer Christopher Morvillo and his wife Neda, and Jonathan Bloomer, the chair of Morgan Stanley International, and his wife Judy, were all reported missing.

AFP journalists in Porticello saw emergency workers moving four body bags from boats returning from the sea into a tent on the quay, or into waiting ambulances.

Several different media outlets later said a fifth body had been found but not yet brought to shore.

In an update late Wednesday, the coastguard confirmed four bodies had been recovered in an "extremely delicate operation".

The depth of the yacht -- which is largely intact and resting on the seabed some 50 metres down -- had been a challenge, it said.

It also noted "the narrowness of the spaces they were exploring and the presence of numerous objects".

"The operation is continuing for the search and recovery of the last two missing," it added, a process that would resume on Thursday morning.

- Five minutes -

Lynch -- an entrepreneur sometimes referred to as Britain's Bill Gates -- had invited the guests onto the yacht to celebrate his acquittal in a massive US fraud case.

The 59-year-old was acquitted on all charges in a San Francisco court in June after he was accused of an $11 billion fraud linked to the sale of his software firm Autonomy to Hewlett-Packard.

Among the survivors was Charlotte Golunski, board director of a company founded by Lynch, who has described how she briefly lost hold of her one-year-old daughter before grabbing her again. Both were plucked to safety.

Fabio Genco, a member of the Palermo Emergency Medical Services who was among the team that treated the child, described the "apocalyptic" situation he found on arriving at the scene.

"The word that the mother and all the injured kept repeating was 'darkness', the darkness that they experienced during the shipwreck," he told the BBC's Newsnight programme.

"They spoke of about five minutes, maybe from three to five minutes, from the moment the boat was lifted, raised by the waves of the sea, until it sank."

He said the survivors rescued had been in shock: "There were truly apocalyptic scenes where everyone was searching and hoping to find the people who at that moment, were not present or just missing."

All the survivors treated in hospital have been discharged, he confirmed.

- Anarchic sea conditions -

The speed with which the yacht sank, and the fact that other boats around it were unaffected, was extraordinary.

Despite eyewitness testimonies that the 75-metre mast had snapped, reports on Wednesday suggested that it was intact.

Some key questions remain, including whether the keel, which provides a counterbalance to the towering mast, was down when the storm hit.

Italian authorities have opened an investigation into what happened and are interviewing all the survivors, including captain James Cutfield, a 51-year-old New Zealander, according to Italian media.

The UK's marine accident investigation branch also sent four inspectors.

Matthew Schanck, from the Maritime Search and Rescue Council, told AFP what happened was a "pretty unprecedented".

UK meteorologist Peter Inness described a waterspout as a "narrow column of rotating air below a thunderstorm that occurs over water".

Like tornadoes, they suck up air in a rotating motion. Many are fairly inconsequential, but some can pack winds of more than 100 kilometres (62 miles) per hour, said Inness.

Jean-Marie Dumon, a former naval officer now with the GICAN, the French maritime industry association, added that conditions with winds of 100kph or more can "create completely anarchic sea conditions which can cause capsizing".

© Agence France-Presse