(AP) -- Florida's governor says the state has concluded that four mysterious Zika infections likely came from mosquitoes in the Miami area.

Gov. Rick Scott said Friday that no mosquitoes in the state have tested positive for Zika. But he says one woman and three men in Miami-Dade and Broward counties likely contracted the virus through mosquito bites.

More than 1,650 Zika infections have been reported in the U.S., but the four patients in Florida would be the first not linked to travel outside the U.S. mainland.

Scott says health officials believe the infections occurred in a small area just north of downtown Miami.

Zika primarily spreads through bites from tropical mosquitoes. In most people, the virus causes only mild illness, but infection during pregnancy can lead to severe brain-related birth defects for the fetus.