Rome — Six people, including two U.S. nationals, a British technology entrepreneur and one of his daughters, were believed to be missing Monday after a large sailing yacht sank off the coast of the southern Italian island of Sicily during a violent storm. The 184-foot Bayesian had been anchored about half a mile off the port of Porticello, near Palermo, with 22 people on board — 10 crew members and 12 passengers.

The vessel sank at about 5 a.m. local time (11 p.m. Eastern, Sunday) after being hit by a possible waterspout spawned by the storm. Italian media said the winds snapped the boat’s single mast, unbalancing the vessel causing it to capsize.

Fifteen of those on board managed to escape the yacht and were rescued by a Dutch-flagged vessel that was anchored in the immediate vicinity. They were brought ashore by Italian Coast Guard and firefighters.

One body — an unidentified male — was recovered, but six people remained missing, the Coast Guard said, including Americans, British and Canadian nationals. Italian media said there were two U.S. nationals among those missing, but CBS News was unable to immediately reach the Coast Guard to confirm that number.

Among the survivors was a 1-year-old British girl who was being treated at a nearby hospital along with her parents. They were doing well, according to Italian media.

“For two seconds I lost my child to the sea, then I immediately was able to grab her again in the fury of the waves,” the girl’s mother, identified only as Charlotte, was quoted as saying by Italy’s ANSA news agency. “I held on to her tightly in the stormy sea. Many were screaming. Luckily the life raft opened up and 11 of us managed to get aboard.”

“It was terrible,” she told ANSA. “In just a few minutes the boat was hit by a very strong wind, and sunk soon thereafter.”

Karsten Borner, the captain of the Dutch vessel that came to the rescue, told ANSA he had been anchored near the Bayesian.

“When the storm was over we noticed that the ship behind us was gone, and then we saw a red flare, so my first mate and I went to the position and we found this life raft drifting, and in the life raft was also a little baby and the wife of the owner.”

A search effort was still underway Monday in the area, with four Coast Guard vessels, a Coast Guard helicopter and a dive team from the national Fire Brigade taking part. The Bayesian appeared to have sunk in an area with a depth of about 160 feet.

According to Italian media, Fire Brigade divers had reached the boat and seen bodies trapped inside some of the cabins.

Witnesses said the boat appeared to have sunk quickly. 

“I was at home when the tornado hit,” fisherman Pietro Asciutto told a local news outlet. “I immediately closed all the windows. Then I saw the boat, it had only one mast, it was very large. I suddenly saw it sink… The boat was still floating, then suddenly it disappeared. I saw it sink with my own eyes.”

The director-general of Sicily’s civil protection agency, Salvatore Cocina, confirmed to CBS News partner BBC News that three of the six people still missing Monday were British tech entrepreneur Mike Lynch, whose company Autonomy Corporation PLC was acquired in 2011 by HP; one of his daughters, Hannah Lynch, who is believed to be 18; and the boat’s chef, Ricardo Thomas.

CBS News has seen corporate documentation showing a company called Revtom, solely owned by Lynch’s wife Angela Bacares, who was among those rescued from the accident, as the owner of the yacht that capsized off Sicily. 

While the yacht was a privately owned pleasure boat, the waters around the island have claimed many lives over the last decade.

Dozens of migrants have died attempting to reach Sicily and smaller Italian islands in the region. Sicily sits only about 100 miles from the east coast of Tunisia in north Africa, and the Mediterranean crossing has been a frequent site of both nautical rescues and disasters as smugglers routinely send small boats overloaded with desperate people into the sea.

contributed to this report.