The F.B.I. ruled out poisoned alcohol as the cause of two American tourists’ deaths in the Dominican Republic in May, bolstering the country’s findings that a spate of tourist deaths this year were not the result of foul play, a State Department spokesperson said on Friday.

The Dominican Republic’s economy relies in part on drawing visitors to its beach resorts, and the country became engulfed in a crisis this summer when the families of multiple American tourists said their loved ones had died under suspicious circumstances. Several had sipped alcohol before their deaths, leading to one theory that tainted drinks were to blame.

The revelation Friday seemed to lend some support to what the Dominican authorities, despite a flood of negative news coverage, had argued: that the deaths, while tragic, were not occurring at an unusual rate. Tourists die on vacation every year, and the State Department has maintained that there has not been an uptick in reported deaths.

F.B.I. investigators did not give their own assessment of the cause of the deaths. They assisted the Dominican Republic National Police by conducting toxicology tests for three cases, including what to many seemed the most suspicious deaths: a couple from Maryland, Nathaniel E. Holmes and Cynthia A. Day, who died overnight in the same hotel room in La Romana.