Divers searching the wreck of a superyacht that sank off Sicily found the bodies of five passengers Wednesday and searched for one more as questions intensified about why the vessel sank so quickly when a nearby sailboat remained largely unscathed.

Rescue crews unloaded three body bags from rescue vessels that pulled into port at Porticello. Salvatore Cocina, head of the Sicily civil protection agency, said two other bodies had also been found in the wreckage for a total of five.

The discovery made clear the operation to search the hull on the seabed 50 metres underwater had quickly turned into a recovery one, not a rescue, given the amount of time that had passed and that no signs of life had emerged over three days of searching, maritime experts said.

The Bayesian, a 56-metre British-flagged yacht, went down in a storm early Monday as it was moored about a kilometre offshore. Civil protection officials said they believed the ship was struck by a tornado over the water, known as a waterspout, and sank quickly.

Fifteen people escaped in a lifeboat and were rescued by a nearby sailboat. One body was recovered Monday — that of the ship's chef, Recaldo Thomas, of Antigua.

Thomas was born in Canada, according to his cousin David Isaac, but would visit his parents' homeland of Antigua as a child, moving permanently to the tiny eastern Caribbean island in his early 20s. Italian officials previously listed Antigua as the nationality of someone on board.

The fate of six missing passengers had driven the search effort, including British tech magnate Mike Lynch, his 18-year-old daughter and associates who had successfully defended him in a recent US federal fraud trial.

Lynch's spokesperson did not respond to a request for comment Wednesday.

Meanwhile, investigators from the Termini Imerese Public Prosecutor's Office were acquiring evidence for their criminal investigation, which they opened immediately after the tragedy even though no formal suspects have been publicly identified.

Questions abound about what caused the superyacht, built in 2008 by Italian shipyard Perini Navi, to sink so quickly, when the nearby Sir Robert Baden Powell sailboat was largely spared and managed to rescue the survivors.

Was it merely the case of a freak waterspout that knocked the ship to its side and allowed water to pour in through open hatches? What was the position of the keel, which on a large sailboat such as the Bayesian might have been retractable, to allow it to enter shallower ports?

“There's a lot of uncertainty as to whether it had a lifting keel and whether it might have been up,” said Jean-Baptiste Souppez, a fellow of the Royal Institute of Naval Architects and the editor of the Journal of Sailing Technology. “But if it had, then that would reduce the amount of stability that the vessel had, and therefore made it easier for it to roll over on its side,” he said in an interview.

The captain of the Sir Robert Baden Powell sailboat, which came to the Bayesian's rescue, said his craft had sustained minimal damage — the frame of a sun awning broke — even with winds that he estimated reached 12 on the Beaufort wind scale, which is the highest, hurricane-strength force on the scale.

He said he had remained anchored with his engines running to try to maintain the ship's position as the storm, which was forecast, rolled in.

“Another possibility is to heave anchor before the storm and to run downwind at open sea,” Karsten Bornersaid in a text message. But he said that might not have been a viable option for the Bayesian, given its trademark 75-metre tall mast.

“If there was a stability problem, caused by the extremely tall mast, it would not have been better at open sea,” he said.

Yachts like the Bayesian are required to have watertight, sub-compartments that are specifically designed to prevent a rapid, catastrophic sinking even when some parts fill with water.

“So for the vessel to sink, especially this fast, you are really looking at taking water on board very quickly, but also in a number of locations along the length of the vessel, which again indicates that it might have been rolled over on its side,” Souppez said.

Italian coast guard and fire rescue divers continued the underwater search in dangerous and time-consuming conditions. Because of the wreck's depth, which requires special precautions, divers working in tag teams could only spend about 12 minutes at a time searching.

The limited dive time is designed in part to avoid decompression sickness, also known as the “bends,” which can occur when divers stay underwater for long periods and ascend too quickly, allowing nitrogen gas dissolved in the blood to form bubbles.

“The longer you stay, the slower your ascent has to be,” said Simon Rogerson, the editor of SCUBA magazine. He said the tight turnaround time suggests the operation's managers are trying to limit the risks and recovery time after each dive.

“It sounds like they're operating essentially on no decompression or very tight decompression, or they're being extremely conservative,” he said.

Additionally, the divers were working in extremely tight spaces, with debris floating around them, limited visibility and oxygen tanks on their backs.

“We are trying to advance in tight spaces, but any single thing slows us down,” said Luca Cari, spokesman for the fire rescue service. “An electric panel could set us back for five hours. These aren't normal conditions. We're at the limit of possibility.”

“It's not a question of entering the cabin to inspect it,” he added. “They've arrived at the level of the cabins, but it's not like you can open the door,” he said.

The Italian coast guard said they had reinforced their dive teams and were using underwater remote-controlled robots, which can stay out for six or seven hours at a time and record the surroundings.

The lack of any signs of life and the recovery of bodies led outside experts to conclude that the search was now a recovery effort and investigation to determine how the tragedy had unfolded.

“I think the fact that there's been quite a lot of diving presence around the vessel and that they haven't been able to pick up any signs of life inside the vessel, is, is unfortunately, not a particularly good sign,” said Souppez. (AP) GRS GRS