FBI toxicology reports ruled out foul play in the deaths of at least three U.S. tourists to the Dominican Republic, the State Department said Friday.

The bureau assisted with the toxicology tests of three of at least nine Americans who fell ill and died while visiting the Caribbean destination earlier this year, CNN reported

Specifically, the FBI determined Nathaniel Holmes, Cynthia Day and Miranda Schaup-Werner each died of natural causes, findings consistent with those of Dominican Republic authorities, USA Today reported.

Schaup-Werner, 41, of Pennsylvania, died in May at the Grand Bahia Principe in La Romana, with Dominican authorities attributing her death to a heart attack. Meanwhile, Holmes, 63, and Day, 49, were found dead in their shared hotel room at the Playa Nueva Romana resort. In that case, Dominican authorities ruled the Maryland couple died of respiratory failure and pulmonary edema, USA Today reported.

A State Department official confirmed to CNN that relatives of the deceased have been notified of the FBI results and issued the following statement: "Our condolences and sympathy go out to the families during this difficult time."

The test results have also been shared with Dominican authorities and ruled out several potential causes of death for the Maryland couple, including methanol poisoning from tainted alcohol, USA Today reported.