A tenth American has died while on vacation in the Dominican Republic over the last 18 months, and the theory some of them died from tainted alcoholic drinks is still being investigated.

Vittorio Caruso, 56, of Glen Cove, Long Island, New York, died June 17 while enjoying his retirement. His sister-in-law said Caruso died after suffering respiratory distress and possibly a heart attack while on vacation.

She said Caruso’s family received a phone call saying the victim was sick. Minutes later, they received a second call telling them he was dead.

The Dominican Republic National Police later confirmed Caruso died from respiratory failure at a hospital in Santo Domingo. They said Caruso had been receiving medical attention since June 11. An autopsy will be carried out.

Dominican officials continue to deny there’s an “avalanche of American tourists dying in our country” and insist the deaths aren’t related. They said some of the Americans died after drinking from a hotel minibar, others died with fluid in their lungs (called a pulmonary edema), while others suffered heart attacks.

Three of the deaths, however, seem to be linked to victims taking a drink from their room’s minibar. On Sunday, the Hard Rock Hotel and Casino in Punta Cana removed liquor dispensers from guest room minibars. Hard Rock claimed their decision was made independently and wasn’t result of two deaths that occurred at its hotels.

By doing this, Hard Rock hopes to "provide more tranquility for guests," said GM Erica Lopez.

U.S. officials also haven’t said the deaths are connected but teams from the U.S. Centers for Disease Control and Prevention (CDC) and the FBI are at the Dominican Republic investigating the deaths.

Seven of the 10 deaths occurred this year.

It began with Robert Wallace, 67, from California who died April 12 after becoming ill at the Hard Rock Hotel & Casino in Punta Cana. His relatives said he was with more than two dozen members of his family for a wedding. A family member said Wallace became sick after drinking scotch from the minibar.

John Corcoran died at the end of April in his hotel room from apparent natural causes. "He loved and frequently visited the Dominican Republic," said his sister.

Miranda Schaup-Werner, a 41-year-old from Pennsylvania, died May 25 shortly after checking into her room at the Grand Bahia Principe resort in La Romana. Weirdly, this was the same room where Nathaniel Holmes, 63, and Cynthia Day, 49, died five days later.

Schaup-Werner was celebrating a wedding anniversary with her husband, Dan. She suddenly fell ill after having a drink from the minibar, said a family member. She collapsed and died a short time later. A preliminary autopsy said she died from a heart attack, pulmonary edema and respiratory failure.

Her death is still being investigated and toxicology results should be released soon.

Holmes and Day, both from Maryland, were found dead by hotel staff on May 30 at the Grand Bahia Principe. Dominican Republic authorities said both Holmes and Day had internal bleeding, including in their pancreases.

Holmes had an enlarged heart and cirrhosis of the liver. Day had fluid in her brain. Both also had fluid in their lungs.

Deaths in Dominican Republic The entrance to the Bahia Principe resort is seen where according to family members a tourist died unexpectedly after getting sick last year on June 20, 2019 in Punta Cana, Dominican Republic. The FBI is assisting the Dominican authorities in the investigation into why tourists are dying. Photo: Joe Raedle/Getty Images

Leyla Cox, 53, from New York City died June 10 in her hotel room at the Excellence Resorts in Punta Cana. Citing a forensics report, the hotel said Cox died from heart attack. Her son disputes this claim.

"I truly believe if she was anywhere else in the world besides the Dominican Republic she'd be alive right now," said her son, Will.

Joseph Allen, 55, from New Jersey died June 13 at the Terra Linda resort in Sosua. His sister said hotel staff found him dead when they checked his room after Allen failed to meet up with his friends. Allen will be autopsied in the U.S.