PALERMO (Reuters) - Italian Navy divers have recovered video surveillance equipment from the superyacht that sank off Sicily last month, killing British tech tycoon Mike Lynch and six other people, a source close to the matter said on Friday.

The recovery of the equipment could help explain why the British-flagged Bayesian went down during a severe and sudden storm off the port of Porticello, near Palermo, on Aug. 19 - an event that has puzzled naval experts.

Lynch's 18-year-old daughter, four guests and the cook died when the 56-metre-long (184-foot) yacht capsized and sank within minutes. Fifteen people, including Lynch's wife, survived and were rescued by a nearby vessel that was unscathed.

The highly specialised divers are combing the wreck on behalf of prosecutors investigating the sinking.

Late on Thursday, they recovered parts of the deck, computer material, video surveillance systems, hard drives and various other equipment, the source said. The electronic devices will be sent to specialised labs outside of Sicily to check their condition and possibly recover data, the source added.

Daniele Governale, a coast guard official in Palermo, said the divers were using a hyperbaric chamber that allowed them to make repeated dives of up to 40 minutes.

The coast guard took underwater images with a remotely operated vehicle that will help draw up a plan to salvage the yacht.

Three crew members, including New Zealand captain James Cutfield, are under investigation for manslaughter and shipwreck. Being investigated does not imply guilt and does not mean formal charges will follow.

Prosecutors have said their investigation will take time, and will require the wreck to be pulled up from the sea bed. The Bayesian is lying on its right side, at a depth of around 50 metres.