A diver has died during preliminary operations to recover British tech tycoon Mike Lynch’s superyacht from the waters off the coast of northern Sicily, local police said.

The accident happened on Friday while the diver was underwater in Porticello, police said, adding the precise cause of death was still unknown.

According to local Italian media, the diver was a 39-year-old Dutch national who worked for a specialist salvage company.

It comes as salvage ships arrived earlier this month to waters off the small port of Porticello, near Palermo, where the Bayesian vessel sank during freak weather last August.

Seven of the 22 people onboard the Bayesian last summer were killed, including Mr Lynch, 59, and his 18-year-old daughter Hannah.

Morgan Stanley International bank chairman Jonathan Bloomer, 70, and his wife, Judy, 71, US lawyer Chris Morvillo, his wife Neda Morvillo and the yacht’s chef Recaldo Thomas, who was originally from Antigua, also died in the sinking on 19 August.

Fifteen people managed to escape on a lifeboat including a one-year-old and Mr Lynch’s wife Angela Bacares.

The cause of the sinking is still under investigation with naval experts saying a yacht of Bayesian’s calibre should have been able to withstand the storm and certainly should not have sunk as rapidly as it did.

The salvage operation is being overseen by British marine consultancy TMC Marine and led by Dutch-based companies Hebo, a maritime services company from Rotterdam, and SMIT Salvage, with support from Italian specialists.

About 70 specialist personnel have been deployed to Sicily from across Europe to work on the recovery operation.

On Thursday, the team said on-site preparations were on schedule and “significant progress” had been made over the past five days.

Analysis of the yacht and the surrounding seabed confirmed there had been no change to its condition since the last inspection, meaning plans to raise the vessel can now go ahead.

Work to move the Bayesian into an upright position and lift it to the surface was scheduled to begin later this month – subject to suitable weather and sea conditions.

Before the vessel is transported to port, sea water will be pumped out of it.

Before the Bayesian is raised it will be held in position by steel slings, as salvage workers detach the vessel’s extensive rigging and 72m (236ft) mast, thought to be one of the tallest in the world.

These will then be stored on the seabed and recovered after the team has recovered the ship’s hull, which investigators say is a primary source of evidence.

There has not been any pollution from the yacht reported, with conditions being monitored and efforts made to secure its tank vents and openings.

Inquest proceedings in the UK are looking at the deaths of Mr Lynch and his daughter, as Mr and Mrs Bloomer, who were all British nationals.

Mr Lynch and his daughter were said to have lived in the vicinity of London, and the Bloomers lived in Sevenoaks in Kent.

The tycoon founded software giant Autonomy in 1996 and was cleared in June last year of carrying out a massive fraud over the sale of the firm to Hewlett-Packard (HP) in 2011.

The boat trip was a celebration of his acquittal in the case in the US.