The Bahamas police said on Tuesday that an investigation into the mysterious death of three Americans in May at a resort on the island of Great Exuma determined they perished due to carbon monoxide poisoning.

Robbie Phillips, 65, and Michael Phillips, 68, of Tennessee; and Vincent Chiarella, 64, of Florida, were found unresponsive at the Sandals Emerald Bay resort, police said in a press conference soon after the incident.

"We can officially confirm that all three of the victims died as a result of asphyxiation due to carbon monoxide poisoning," the police said in a statement. "This matter remains under active investigation."

In response to a Reuters request for comment, Sandals Resorts said: "We have fully supported the investigation into this event to ensure we are doing everything possible to learn from it."

The company added that "CO detectors have now been placed in all guest rooms at Sandals Emerald Bay."

Robbie and Michael Phillips, who were married, had complained of illness the prior evening and visited a local medical facility.

Chiarella's wife, who was staying with Chiarella in a separate villa from the Phillips, was also airlifted and taken to the hospital in serious condition but ultimately survived.