ROME (Reuters) -The sinking of a luxury yacht on Aug. 19 off the northern coast of Sicily left seven people dead, including British tech tycoon Mike Lynch, his daughter Hannah and Morgan Stanley's Jonathan Bloomer.
Here is what we know about the accident.
VIOLENT STORM
The Bayesian, a British flagged 56-metre (184-feet) superyacht, was anchored off the port of Porticello, near Palermo, when it sank in the pre-dawn dark amid a very severe and sudden weather event.
Prosecutor Raffaele Cammarano said on Saturday the event was most likely a "downburst", a very strong downward wind that is an intense but relatively frequent event at sea, rather than a waterspout which involves rotating winds like a tornado.
The coast guard said that given the weather forecast, there was nothing wrong about the Bayesian being moored offshore rather than at sheltering at port. Another yacht anchored nearby emerged from the storm unharmed.
Twenty-two people were on board, and 15 survived, including nine out of 10 crew members as well as Lynch's wife, whose company owned the Bayesian. They were found on a life raft. Six out of the 12 passengers died.
Prosecutors, who have put the yacht's captain James Cutfield under investigation for manslaughter and shipwreck, said the ship would have to be pulled out of the water before the investigation could be concluded.
STERN FIRST WENT DOWN
The Bayesian sent its last signal before sinking via the tracking Automatic Identification System (AIS) at 0206 GMT, according to the MarineTraffic website.
Chief Prosecutor Ambrogio Cartosio said a red flare alerting rescue services about the emergency was fired into the sky at 0238 GMT, more than 30 minutes after the boat had gone down.
The head of Palermo's Fire Brigade, Girolamo Bentivoglio Fiandra, said the boat sank from the stern and is lying on its starboard side at a depth of around 50 metres (164 feet).
In the yacht, the bodies of the dead were found in the cabins on the left-hand side of the boat, where the passengers may have tried to search for remaining bubbles of air, he added.
Prosecutor Cammarano said the passengers were all probably asleep at the time of the storm which was why they failed to escape.
'INCOMPREHENSIBLE'
The sinking has puzzled seafarers and nautical engineers, who have said that it should have taken hours for the Bayesian to fill up with enough water to sink it, making its swift demise incomprehensible.
There have been suggestions that one or more portholes, windows or other openings may have been inadvertently left open by the crew, or broken or smashed by the storm, letting in water.
Experts also wondered if the yacht had been moored with its keel up, potentially compromising its stability. The keel is a fin-like stabilising structure under the hull, which can be partially lifted to reduce the depth of the boat in shallow waters or harbours.
Prosecutors have said it was too early to comment on either hypothesis. They also said crew members were not immediately tested for alcohol or drugs because they were in a state of shock when rescued.
UNSINKABLE
The Bayesian was built in 2008 by Perini Navi, an Italian luxury yacht maker. It featured the world's tallest aluminium mast, measuring 72 metres, but early reports that the mast broke in the storm have so far proven unfounded.
Giovanni Costantino, CEO of the Italian Sea Group, which owns Perini, said the yacht was "one of the safest boats in the world" and basically unsinkable.
He alleged that the sinking was due to a chain of human errors given that the storm was expected. He made his assertions partly based on data from the Automatic Identification System. The captain and other crew members have not spoken publicly about the disaster and attempts by Reuters to reach them have been unsuccessful.
Costantino said that had the crew shut all doors and hatches, turned on the engine, lifted the anchor, lowered the keel and turned the yacht to face the wind, it would have suffered no damage.
He added that data showed it took 16 minutes from when the wind began buffeting the yacht, and it began taking on water, for it to sink.
Reuters has not been able to confirm his assertions.