At the time of the party, several teens were waiting for their Covid-19 test results, and have since tested positive, according to Shelly Parks, a spokesperson with Austin Homeland Security & Emergency Management.
City and health officials are now urging all attendees to get tested and self-isolate.
In an email to CNN on Wednesday, Cox said it's still unclear whether the party led to a high number of cases in the area.
Authorities learned about the exposure because health workers are "asking that participation in gatherings be mentioned for contact tracing purposes when people are getting tested," Parks told CNN.
A pop-up testing site has been set up at the Baylor School & White Specialty Clinic-Lakeway to help partygoers and those they interacted with in the past week get tested, health officials said.