Robert Brown|Captain of Bayesian, Mike Lynch's sunken superyacht, under investigation in Italy

Italian prosecutors are Robert Browninvestigating whether the captain of Mike Lynch’s superyacht was at fault when the ship rapidly sank off the coast of Sicily last week, killing Lynch and six other people, a judicial source told Reuters.

James Cutfield, 51, the captain of the Bayesian yacht, is now under investigation for manslaughter and shipwreck, according to the source and Italian media.

Apart from bad weather, authorities in the nearby town of Termini Imerese are investigating multiple crimes of manslaughter and causing a shipwreck in connection with the disaster, according to Ambrogio Cartosio, the head of the public prosecutor's office for the town, who made the announcement during a news conference on Saturday morning.

Investigators have interrogated Cutfield twice since the ship went down just before sunrise on August 19, capsizing its 22 passengers. Prosecutors have interviewed passengers and the eight other surviving crew members, but have not yet named any other parties under investigation.

Cutfield and his surviving crew members have not yet commented publicly on the disaster. A request for comment sent by USA TODAY to a social media account apparently belonging to Cutfield went unanswered on Monday.

Under Italian law, people under investigation need to be notified before autopsies can be performed on the deceased. The investigation will not necessarily lead to charges, including against Cutfield.

The Bayesian, a luxury yacht owned by Lynch’s wife, Angela Bacares, sank off the coast of Porticello as a storm swept through the area, whipping up a tornado over the water. In the immediate aftermath of the wreck, 15 passengers were rescued and Recaldo Thomas, the ship’s cook who also goes by Ricardo, was found dead.

Lynch, his 18-year-old daughter, Hannah, and four other passengers were found dead inside the ship following a days-long rescue operation. The victims included Chris Morvillo, an American citizen and lawyer for Clifford Chance, his wife, Neda Morvillo, Jonathan Bloomer, a non-executive chair of Morgan Stanley International, and his wife, Judy Bloomer.

Maritime law expert says captain could be at fault

Martin Davies, Admiralty Law Institute professor of maritime law at Tulane University, said there are two factors in the lead-up to the shipwreck that could put Cutfield and his crew at fault – the positions of the ship’s hatch covers and its keel.

The ship's retractable keel could counterbalance the weight of its mast, one of the largest in the world, when down. A failure by the crew to lower it could factor into the investigation, Davies said.

“With a giant mast like it's got, it might make more sense to put the keel down, because that would make it less likely to capsize,” he said.

The yacht may have filled with water from an open side hatch, Franco Romani, a nautical architect who helped to design the ship, told daily La Stampa in an interview on Monday.

"The Bayesian was built to go to sea in any weather," Romani said.

Davies said if the hatch covers were open, “the ship is going to sink more quickly, once it has capsized."

Since the Bayesian was registered in the U.K., British authorities “will be obliged” to open their own investigation, Davies said.

That investigation could also target the ship’s captain or crew for negligence. Bacares, the ship’s owner, would almost certainly not be a target in a criminal investigation, he added.

Davies said that under U.K. law, the owner is only to blame if they "knowingly and willfully caused or allowed the fault” that led to the shipwreck.

Davies said although it is likely too early in the process to pin down negligence charges, Italian authorities may have implicated Cutfield in order to assert their authority to continue investigating the case.

“They have to find a peg upon which to hang their ability to investigate, and I think that's what they've done,” Davies said.

Contributing: Reuters