The CDC designated Bronsville as a "yellow" area "where local spread of Zika virus has been identified, but there is not yet any evidence of widespread, sustained local spread.
"Although the specific level of risk in yellow areas is unknown, there is still a risk to pregnant women," the group warned.
The CDC's announcement came after four new cases of locally-transmitted Zika were confirmed last week. The first case in the Brownsville area was discovered on November 28.
The new cases involve three men and one woman, who is not pregnant, reported KRGV, an ABC affiliate. The confirmed infections include two minors who lived in close proximity to the woman diagnosed with the virus in November, who was also not pregnant.
“Right now, we’re aware that local transmission has occurred in a small area of Brownsville,” said Dr. John Hellerstedt, commissioner of the Texas Department of State Health Services. “However, we want to cast a wide net with testing to develop a clearer picture of what is happening with Zika in the area and provide pregnant women with more information about their health.”
Texas health officials are recommending all pregnant Brownsville residents and those who have traveled there on or after October 29 be tested for Zika.
ABC News' Gina Sunseri contributed to this report.