Emergency workers in southern Italy are still hunting for six people missing after a tornado sank a luxury yacht early Monday - prompting an air and naval operation off the coast of Sicily. Fifteen people were rescued from the wreckage, according to Italy's Coast Guard. One body was recovered on Monday and four more on Wednesday, after divers struggled to reach deep inside the yacht around 50 meters underwater (approximately 150 feet).

Two Americans and four Britons were among the six initially reported missing - including British tech tycoon Mike Lynch, Jonathan Bloomer, chairman of Morgan Stanley International, and Chris Morvillo, a prominent lawyer. Here's what we know. What happened? A small waterspout - a type of tornado - spun over the Mediterranean island early Monday, likely capsizing the sailing boat amid lashings of rain and strong thunderstorms.

The British-flagged yacht, called the "Bayesian," was anchored about a half a mile from the port of Porticello, on Sicily's northern coast. The vessel sank after its mast broke in half in the storm, Salvatore Cocina, head of Sicily's Civil Protection, told CNN on Tuesday. Eyewitnesses described furious gales and hurricane-like winds that left an avalanche of debris near the pier.

More than a dozen survivors were spotted in the area hanging onto life rafts, according to the captain of a nearby boat, who steadied his ship to avoid colliding with the Bayesian. "We got this strong hurricane gust and we had to start the engine t.