A probable case of local transmission of the Zika virus has been reported in Texas, state health officials announced on Monday, making it the second state, after Florida, in which the infection is thought to have been carried from person to person by mosquitoes.

The patient is a woman who is not pregnant and lives in Brownsville, on the Gulf Coast near the Mexican border. The state’s first case of chikungunya, a virus spread by the type of mosquito that carries Zika, was confirmed this year in Brownsville.

Medical investigators must now determine whether the infection is spreading and, if so, how many people may have become infected. Officials have begun asking the woman’s neighbors for urine samples and trapping mosquitoes to test for the virus.

State and county health officials are working with the Centers for Disease Control and Prevention on the case. The state medical operations center has been activated to help with contact tracing, mosquito surveillance and public education.