SAN JUAN, Puerto Rico — Samples extracted from three American tourists who died at a resort in the Bahamas under mysterious circumstances have been sent to a lab in the United States to expedite results and help authorities understand what happened, officials said Monday.

The police commissioner of the Bahamas, Paul Rolle, said officials also collected samples from the rooms where the tourists were staying and the surrounding property to determine whether any contaminants were present.

“We really want to know what caused this,” he said.

He identified the victims as Michael Phillips, 68, and wife Robbie Phillips, 65, of Tennessee, and Vincent Paul Chiarella, 64, of Florida. Rolle declined to provide their hometowns.

Chiarella’s wife, Donnis, was airlifted to a hospital in Florida and remains in serious condition, Rolle said.

Their bodies were found Friday morning at the Sandals Emerald Bay resort in Exuma, where the couples had been staying in two separate villas.

The samples were sent to a lab in Philadelphia, with results of the toxicology study expected in about a week, Rolle said. He noted that the Bahamas’ Department of Environmental Health and police officers are still at the resort.

When asked what he thinks might have caused the tourists’ deaths, Rolle said: “I’m not going to speculate.”

He noted that all four tourists went to a doctor the night before their bodies were discovered and they had complained of feeling ill. He said they went at different times and had eaten different things.

Meanwhile, Sandals Resorts said it would not comment further beyond its original statement, which noted that it is supporting the investigation and the families of those affected.

“Out of respect for the privacy of our guests, we cannot disclose further information at this time,” the company said.

The deaths come seven years after a Delaware family became seriously ill at a resort in the U.S. Virgin Islands. U.S. authorities determined that methyl bromide, a highly toxic pesticide banned for indoor residential use in 1984, was to blame and had been used at that resort several times.

Associated Press reporter Michael Catalini in Trenton, New Jersey, contributed.