The FBI is working with Dominican authorities in the investigation of recent tourist deaths, according to the US Embassy in the Dominican Republic.
The FBI is assisting in further toxicology analysis of the deaths that took place at the Bahia Principe in La Romana. The agency said the results could take up to a month.
The Embassy in Santo Domingo said in a statement last week that the two governments are working together to ensure that US travelers are safe.
"The safety and security of US citizens that live in, work in, and visit the Dominican Republic remains our highest priority. These incidents are tragic and we offer our deepest condolences to those personally impacted,"Ambassador Robin Bernstein said according to the statement.
Officials ask that the public be patient as the investigations unfold.
At least nine American citizens have died since June 2018 at a Dominican Republic resort or after becoming ill at one, according to the US State Department, victims' relatives and the resorts involved.
Within a week, three tourists died in May at the Grand Bahia Principe in La Romana. A couple, Nathaniel Holmes and Cynthia Day, were found dead in their hotel room on May 30. Both had internal bleeding and fluid in their lungs, Dominican authorities said. Five days earlier, Miranda Schaup-Werner died in her hotel room after having a drink from the minibar, family spokesman Jay McDonald told CNN affiliate WFMZ .
At least six other Americans died in the past 13 months during resort stays or after becoming ill there.
Robert Wallace and David Harrison both died during or after stays at the Hard Rock Hotel & Casino in Punta Cana, their relatives said. Wallace died in April, his relatives told CNN affiliate KTXL , while in the country for a wedding. Harrison died in July, according to his widow, Dawn McCoy.
In June 2018, Yvette Monique Sport died at the Bahia Principe in Punta Cana, her sister told CNN.
Leyla Cox also died in Punta Cana. She died June 10 in her hotel room at the Excellence Resorts.
Joseph Allen died three days later in his hotel room at the Terra Linda resort in Sosua after not feeling well, his sister Jaimie Reed told CNN.
Businesswoman and "Shark Tank" star Barbara Corcoran , said her brother died in his hotel room in the Dominican Republic at the end of April from what is believed to be natural causes.
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 country from something other than natural causes, according to US State Department statistics . That averages about 18 annually.
Dominican Republic leaders maintain the country is one of the region's top tourism destinations, with more than 6 million tourists last year, including 2.2 million Americans, according to the Caribbean Tourism Organization.
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."