Tech tycoon Mike Lynch drowned and the causes of the deaths of three other British nationals remain under investigation following the sinking of the Bayesian superyacht off the coast of Sicily, a series of inquest openings in the UK heard.

Billionaire entrepreneur Dr Lynch, 59, his daughter Hannah Lynch, 18, Morgan Stanley International bank chairman Jonathan Bloomer, 70, and his 71-year-old wife Judy Bloomer were among those on the stricken vessel.

Detective Superintendent Mike Brown of Suffolk Police said their deaths came after the Bayesian “for reasons yet to be unascertained sank rapidly” between 4.15am and 4.45am on August 19.

He said that searches began in the following hours and “continued uninterruptedly in the following days”, with bodies later located in the cabins of the vessel.

The officer said the time of death for all four was recorded as 5am the same day.

Each of the four inquests were separately opened and adjourned in Ipswich on Friday, until a hearing on April 15 next year.

Mr Brown said the Bayesian was 0.8 nautical miles from the coast of the fishing village of Porticello at the time and had 22 people on board – 12 crew and 10 guests.

Seven of them died, and inquests into the deaths of the four who were British nationals have now been opened.

Mr Brown said Dr Lynch’s provisional medical cause of death was recorded as drowning following a post-mortem examination by Professor Antonia D’Argo.

He said that his death was confirmed on August 22 following the recovery of his body.

He said that the medical cause of death remained under investigation in the cases of Hannah Lynch and Mr and Mrs Bloomer following post-mortem examinations by Dr Tomasso D’Anna.

He said that the deaths of Mr and Mrs Bloomer were confirmed on August 21, and Miss Lynch’s death was confirmed on August 23, following the recovery of their bodies.

The officer said an investigation had been started by the Marine Accident Investigation Branch (MAIB) to “understand how the Bayesian sank” and the Italian authorities have started “their own independent criminal investigations”.

Dr Lynch and his daughter both lived in the vicinity of London, while the Bloomers lived in Sevenoaks in Kent, Mr Brown said.

The others who died, in addition to the four British nationals, were US lawyer Chris Morvillo and his wife Neda Morvillo, and Canadian-Antiguan national Recaldo Thomas who was working as a chef on the vessel.

Suffolk’s senior coroner Nigel Parsley asked Mr Brown if “in effect we’re in the hands of” the MAIB and the Italian authorities as to “when we will get any further material”.

The officer replied: “Yes.”

The coroner adjourned proceedings until April 15 “for further work” to be carried out.

Dr Lynch had founded software giant Autonomy in 1996 and was cleared in June this 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.