James Cutfield, a 51-year old New Zealand citizen, is being investigated for possible manslaughter and culpable shipwreck, Italian dailies reported.
Under Italian laws, being under investigation does not imply being guilty and does not necessarily lead to criminal charges.
Prosecutors in Termini Imerese did not reply to calls to confirm the reports.
On Saturday, chief prosecutor Ambrogio Cartosio confirmed an investigation had been launched but said a suspect had not been identified.
He said his team will consider each possible element of responsibility including those of the captain, the crew, individuals in charge of supervision and the yacht's manufacturer.
Cutfield was among 15 survivors of the sinking that killed UK tech magnate Mike Lynch, his daughter Hannah and five others.
The Bayesian, a 56-metre luxury yacht, went down near the Mediterranean island in southern Italy last Monday.
Investigators are focusing on how a sailing vessel deemed "unsinkable" by its manufacturer, Italian shipyard Perini Navi, sank while a nearby sailboat remained largely unscathed.
Prosecutors said the event was "extremely rapid" and could have been a "downburst" - a localised, powerful wind that descends from a thunderstorm and spreads out rapidly upon hitting the ground.
The crew was saved, except for the chef, while six passengers were trapped in the hull.
8°C