Florida's governor on Friday reported the first evidence of local Zika virus transmission in the continental United States, saying testing of four residents showed they were likely infected by mosquito bites.

Governor Rick Scott said the state believed active transmission of the virus was occurring in a small area of the populous Miami-Dade county. One case involved a woman and the other three involved men, Scott said.

While health officials have yet to identify mosquitoes carrying the virus, the state has ruled out other means of transmission, including travel to another country with a Zika outbreak, and sexual contact.