Authorities in the eastern Caribbean said they are trying to locate two people believed to be US citizens who were aboard a yacht that was hijacked by three escaped prisoners from Grenada.

The Royal Grenada Police Force said in a statement released on Friday that they were working on leads “that suggest” that the two occupants of the yacht may have been killed.

“This investigation is in its infancy stage,” police said.

The non-profit Salty Dawg Sailing Association identified the owners as Ralph Hendry and Kathy Brandel.

It said they are “veteran cruisers” and longtime members of the association, calling them “warm-hearted and capable”.

The association said that a cruising skipper had contacted the association about a member’s yacht, Simplicity, that was found “anchored and abandoned” off a beach on the island of St Vincent.

“The good Samaritan had boarded the boat and noted that the owners … were not onboard and found evidence of apparent violence,” the association said in a statement.

The association said Hendry and Brandel had sailed the yacht in last year’s Caribbean Rally from Hampton, Virginia, to Antigua, and were spending the winter cruising in the eastern Caribbean.

“This is a very upsetting event and details are still unconfirmed by the authorities, but this does appear to be a tragic event,” said Bob Osborn, the association’s president.

“In all my years of cruising the Caribbean, I have never heard of anything like this.”

Authorities in Grenada said they dispatched senior investigators and a forensic specialist to the nearby island of St Vincent, where the escaped prisoners were arrested on Wednesday.

The prisoners, ages 19, 25 and 30, were charged a couple of months ago with one count of robbery with violence.

The eldest inmate also was charged with one count of rape, three counts of attempted rape and two counts of indecent assault and causing harm, police in Grenada said.

The three men escaped from their holding cell on February 18, according to police.

Authorities said a preliminary investigation suggests that the three men seized the yacht from Grenada’s capital, St. George’s, and travelled to St Vincent.

The owners of the yacht have not been identified.

—AAP