Authorities have detected Zika in mosquitos in Miami Beach, the first time the insects have been found carrying the virus in the United States.
"These findings are very disappointing, but not surprising," the Florida Department of Agriculture and Consumer Services said in a statement released on Thursday.
Officials had already suspected that the virus was being spread by mosquitos locally following a recent outbreak of the virus in Miami.
The Centers for Disease Control and Prevention have warned pregnant women against travelling to Miami as the virus can cause birth defects.
Last week the US Food and Drug Administration also instructed blood banks across the country to screen donated blood for Zika.