(CNN) Samples taken from at least one minibar at the Bahia Principe Hotel are being tested by the FBI as part of the agency's collaboration with Dominican Republic authorities, Ministry of Health communications director Carlos Suero said Wednesday.

Suero added that an extensive collection of samples is taken by Domincan authorities when someone dies in a hotel room. Minibars are tested for bacteria and water from showers and sinks are examined, he said.

The FBI is assisting with the toxicology tests of three of the nine Americans who have died in the Dominican Republic in the past year, he said.

Last week the US Embassy announced the FBI involvement in toxicology analysis and said results might take up to 30 days.

The spate of deaths has left many Americans wondering if they should cancel their upcoming trips to the Caribbean paradise.

Officials in the Dominican Republic have called the deaths isolated events as they work to reassure travelers their country is safe

The family of one of the American tourists who died there in recent months wants pathologists in the United States to examine his body for a cause of death, his brother told CNN on Wednesday.

Joseph Allen, 55, of New Jersey, was found dead last week in his hotel room, his family said, making him at least the ninth US tourist to die at a Dominican Republic resort , or after becoming ill at one, over the past 13 months.

Preliminary autopsy results suggest Allen suffered from cardiac arrest, and there we no signs of violence, according to a report Dominican authorities gave to CNN.

But a doctor had just given Allen a clean bill of health during a physical, his brother, Jason Allen, told CNN's "New Day," adding that he is having a hard time understanding how Joseph could have died suddenly. The family is arranging for the body to return to the US.

"If we don't feel like we're getting the help we need from (Dominican authorities) and the answers we need from them, we'd like to get some kind of testing done on American soil by American doctors to help us to understand what could have been the cause of my brother's death," Jason Allen said.

Of the nine Americans who have died while or after visiting a Dominican Republic resort since June 2018, it's not clear how many deaths owed to natural causes.

"In the last five years, over 30 million tourists have visited the Dominican Republic, but this is the first time the international media report such an alarming situation," Tourism Minister Francisco Javier Garcia said earlier this month. "These are isolated incidents, and the Dominican Republic is a safe destination."

What we know about Joseph Allen's death

Joseph Allen was a repeat guest of the Hotel Terra Linda in the coastal Dominican city of Sosua, and he was there last week with friends, Jason Allen told HLN on Tuesday . The resort was Joseph Allen's spot, "his Cheers," the brother said, referring to the legendary sitcom pub.

Joseph Allen died June 13 after falling ill in the Dominican Republic, his family says.

Allen's friends told the family that he'd complained last Wednesday about not feeling well.

"He complained about being really hot," Jason Allen told CNN. "His friend looked at him -- he was sweating bullets. (Joseph) took a shower, cooled off, said he felt a lot better.

"He was going to hang out that night (but) decided, 'You know what, I feel better, but I don't feel well enough to go hang out, so I'm just going to relax in the room and read.'"

Hotel staff found him dead in his room early Thursday after friends expressed concern that he hadn't met up with them that morning, his sister, Jaimie Reed, told CNN.

Jason Allen has no reason to believe his brother was killed intentionally, he said. But he wonders if anything at the hotel -- the air, the drinks -- contributed to his death.

"What I do know is that I want no one and their family to endure what we're enduring right now," he told HLN.

At least 9 died on vacation

Besides Joseph Allen on June 13, the deaths of American citizens during or after stays at Dominican Republic resorts in the last 13 months include these cases:

• Leyla Cox, 53, of New York City, died June 10 in her room at the Excellence Resorts in Punta Cana.

The cause of death was heart attack, the hotel stated, citing a forensics report. CNN has not independently confirmed the contents of the report.

Cox's son expressed doubts over the hotel's claims about his mother's cause of death, saying he did not believe she died from "natural causes."

• Miranda Schaup-Werner, 41, of Pennsylvania, and, days later, Nathaniel Holmes, 63, and Cynthia Day, 49, a couple from Maryland, died in May at the Grand Bahia Principe in La Romana.

Schaup-Werner died in her hotel room after having a drink from the minibar, family spokesman Jay McDonald told CNN affiliate WFMZ . She suffered a heart attack, pulmonary edema and respiratory failure, a preliminary autopsy cited by the Attorney General's Office of the Dominican Republic showed. The death remains under investigation, and toxicology results are pending.

At the same hotel, Holmes and Day were found dead in their hotel room on May 30. Both had internal bleeding, including in their pancreases, according to Dominican authorities. Holmes had an enlarged heart and cirrhosis of the liver -- both signs of significant pre-existing disease, the Dominican authorities said, and Day also had fluid in her brain.

Holmes and Day also had fluid in their lungs, Attorney General Jean Alain Rodriguez Sanchez's office said in a statement.

Authorities won't provide more details on the causes of the couple's deaths until toxicology results are completed, they said.

The FBI is assisting in further toxicology analysis of the three deaths that took place at the Bahia Principe in La Romana, and the results could take up to a month, the US Embassy in Santo Domingo said last week

• John Corcoran, the brother of "Shark Tank" TV star Barbara Corcoran, died at the end of April in his hotel room in the Dominican Republic, according to a statement from his sister.

"He passed away from what is believed to be natural causes," the statement said. "He loved and frequently visited the Dominican Republic."

Robert Wallace, 67, died on April 12 after becoming ill April 12 at the Hard Rock Hotel & Casino in Punta Cana, relatives told , died on April 12 after becoming ill April 12 at the Hard Rock Hotel & Casino in Punta Cana, relatives told CNN affiliate KTXL . Wallace became sick after drinking scotch from a minibar, Tommy Tickenhoff, his son-in-law, told the station.

• David Harrison, 45, died in July 2018 at the Hard Rock Hotel & Casino in Punta Cana, according to his widow, Dawn McCoy. This is the same place where Wallace would fall ill nine months later.

Harrison said he wasn't feeling well when he returned from a snorkeling excursion, McCoy said. The next morning, he was sweating and unable to get up before he died. The cause of death was listed as a heart attack and pulmonary edema by local authorities.

Yvette Monique Sport, of Pennsylvania, , of Pennsylvania, died in June 2018 at the Bahia Principe hotel in Punta Cana, her sister told CNN.

After having drinks with her fiance, Sport took a shower and went to bed, Felecia Nieves said. She also had a drink from the minibar. Her fiance heard her make "a gurgling sound" in her sleep, Nieves said. The next morning, he discovered she was dead, Nieves said. The family is still awaiting toxicology reports.

Officials say destination is safe

Officials in the Dominican Republican or the US have not said the deaths are connected.

The State Department has a standing travel advisory for the Dominican Republic, urging travelers to have caution because of crime, but it has not issued a travel alert specific to the traveler deaths.

From 2012 to 2018, 128 Americans died in the Dominican Republic from something other than natural causes, according to US State Department statistics . That averages about 18 annually.

The Dominican Republic is one of the Caribbean's top tourism destinations, with more than 6 million stopover tourists last year, including 2.2 million Americans, according to the Caribbean Tourism Organization.

Jamaica (1.6 million) and the Bahamas (1.3 million) were second and third, respectively, among Caribbean nations for the number of stopover American tourists in 2018, the CTO says.

In Jamaica, 135 American tourists died from something other than natural causes from 2012 to 2018, according to the US State Department. The number for the same time period in the Bahamas was 107.

The Dominican Republic is the "largest, fastest growing, tourism destination of the Insular Caribbean," government spokesman Roberto Rodriguez Marchena said in a video, adding that 14 million Americans have visited since 2012.

"In the last five years, over 30 million tourists have visited the Dominican Republic, but this is the first time the international media report such an alarming situation," Tourism Minister Francisco Javier Garcia said this month. "These are isolated incidents and the Dominican Republic is a safe destination."