State officials have announced four more cases of Zika that are believed to have been transmitted in Texas, almost two weeks after announcing the first such case.

That first case, announced Nov. 28, was a woman who lives in Brownsville, a town located on the Mexico border. The Texas Department of State Health Services said Friday that the new cases were identified in tests conducted after her infection was uncovered.

Health officials are still investigating, but say the additional infections were likely also acquired in Brownsville, near her home. Health officials say the additional people were likely infected before mosquito control efforts intensified in the area.

None of those infected are pregnant. Infection during pregnancy can lead to severe brain-related birth defects.