The bodies of the two British crewmen and two passengers, an American couple living in Jersey, were found two days after the cash was withdrawn on Antigua in the Leeward Islands.
All the victims had been tied up and gagged with masking tape before being repeatedly stabbed in the face, head and neck. They were discovered on Saturday on the Computacenter Challenger, moored off Barbuda, a nearby island.
The professional crewmen who died were Ian Cridland, 35, a former geologist, and Thomas Williams, 22, both from the Southampton area. The passengers were John Cleaver, 58, a computer company executive, and his wife Patty, 52.
Yesterday, it emerged that somebody from the yacht, probably one of the crew, had withdrawn dollars 10,000 (pounds 6,850) from a bank last Thursday to pay for fuel, harbour charges and other expenses.
The yacht then sailed to Barbuda, 15 miles away, where it anchored at the western end of the island. The bodies were found by tourists on another boat, who became suspicious when they saw no movement on board for two days. Alvin Goodwin, deputy police commissioner for Antigua and Barbuda, refused to reveal whether the money was missing when officers boarded the yacht. He said: 'We are keeping an open mind on the case.'
However, a Foreign Office spokesman in London said: 'The yacht had taken on board a fairly substantial float in cash, about dollars 10,000 American. It may have been that robbers saw this.'
Mr Goodwin said that there was no evidence that drug-smugglers had been involved in the murders: 'We have made a couple of busts across the area, but there is no large-scale drug-trafficking here.'
Mr Cleaver, who came from California, administered property in Jersey, owned by Computacenter Ltd, a London computer firm. He and his wife had decided to take a holiday aboard the 65ft yacht, which is owned by Innovative Entertainment and Promotions Ltd, a sister company.
The boat is used for corporate entertainment and Mr Cridland, who lived with his girlfriend when he was in Britain, and Mr Williams were full-time crewmen.
Martin Hellawell, a spokesman for Computacenter, said: 'We are absolutely devastated. They were all people who were well-known within the company and we can't believe the horrible way in which it happened.'
Three Scotland Yard detectives who were already in Antigua to investigate the murder last year of the former head of Customs, are helping the inquiry. Forensic scientists will fly out from Britain to examine the bodies and the yacht.
Serious crime is rare on Antigua and Barbuda. A Foreign Office spokesman said: 'The murder rate in Antigua is virtually negligible, and the inhabitants of the islands are naturally shocked at a crime of this magnitude.'
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