The authorities in the Eastern Caribbean said they are trying to locate two people believed to be American citizens who were on a yacht hijacked by three escaped prisoners from Grenada.

The Royal Grenadian Police Force said in a statement issued on Friday that it is working on leads "indicating" that the yacht riders may have been killed, noting that the investigation is still in its early stages.

The nonprofit Salty Dawg Sailing Association identified the owners as Ralph Hendry and Cathy Brandel. It said they were "seasoned adventurers" and longtime members of the association, describing them as "kind-hearted and capable."

The association said a skipper contacted the association regarding the yacht of a member, Simplicity, which was found "moored and abandoned" off the coast of Saint Vincent island.

The association said in a statement on Thursday: "The skipper boarded the boat and noticed that its owners... were not on board and found evidence of obvious violence."

The association said Hendry and Brandel sailed the yacht in the Caribbean Rally last year from Hampton, Virginia, to Antigua and were spending the winter trip in the Eastern Caribbean.

Bob Osborne, the association's president, said: "This is a very disturbing incident and details are still uncertain by the authorities, but it appears to be a tragic event." "In all my years of sailing in the Caribbean area, I have never heard of anything like this."

Family members of the missing met with authorities in Saint Vincent on Saturday, where they were seen boarding the hijacked yacht. It was guarded by officials, one of whom was wearing rubber gloves.

The Hendry family issued a statement on Saturday thanking the police, the local coast guard, and everyone who helped the authorities gather information.

The family said: "It means a lot to us that so many people cared for Ralph and Cathy as friends and colleagues, and that they were willing to stop and help in any possible way."

They also asked all those trying to conduct independent searches to "stand down."

The family said: "The only way we feel this situation can become worse is if anyone is injured or endangered while attempting to conduct searches."

The authorities in Grenada said they sent senior investigators and a forensic specialist to the nearby island of Saint Vincent, where the escaped prisoners were apprehended on Wednesday.

The prisoners, aged 19, 25, and 30, were charged two months ago with one count of robbery with violence. Grenadian police said the oldest prisoner was also charged with three counts of attempted rape and two counts of indecent assault and causing harm.

The police said the three men escaped from their cell on February 18.

The authorities said the preliminary investigation indicates that the three men took over the yacht in St. George, the capital of Grenada, and traveled to Saint Vincent.