The governor says the state has concluded that four Zika infections have likely come from mosquitoes in the Miami area.
He says no mosquitoes in the state have tested positive for Zika, but one woman and three men have likely found the virus through mosquito bites.
Health department officials believe the transmissions have happened in a small area just north of downtown Miami.
Federal authorities have told blood centers in the area to suspend collections because of investigations into Zika cases. These may account for the first infections that mosquitoes have spread in the continental U.S.