Health officials are testing mosquitoes in Miami-Dade County, after a Floridian woman tested positive for the Zika virus.
Florida's Department of Health and the U.S. Centers for Disease Control and Prevention have not confirmed the reason for their investigation.
The woman reportedly has no apparent connection to travel outside the country, which would be a first for Zika in the United States.
"Mosquitos have been trapped in the area of investigation and are being tested," was all the detail Health Department spokeswoman Mara Gambineri would give in an email Wednesday to The Associated Press.
Although more than 1,300 Zika infections have been reported in the U.S., none were connected to bites from local mosquitoes.
This worrying discovery may mean that Zika has invaded the continental U.S.