Three American tourists found dead inside two villas at a luxury Sandals resort in the Bahamas earlier this month were killed by carbon monoxide poisoning, according to local news reports.

Vincent Paul Chiarella, 64, of Florida, Michael Phillips, 68 and his wife Robbie Phillips, 65, from Tennessee, were found dead in the villas on May 6 at the adults-only Sandals Emerald Bay Resort on Great Exuma.

Both the Tribune and The Nassau Guardian newspapers are reporting that their cause of death was carbon monoxide poisoning. The autopsy and toxicology reports are expected to be released soon, according to the newspapers.

Chiarella’s wife, Donnis, 65, was taken to a hospital in Nassau and was then airlifted to Kendall Regional Hospital in Miami-Dade County. The Chiarellas, who own a home in Panama City Beach, Florida, were reportedly celebrating their anniversary at the resort.

All four had fallen ill shortly before their deaths, and had gone to the clinic, at different times, to get treatment. Their villas were next to each other in the same building at the resort, according to the Nassau Guardian.