San Antonio Mayor Ron Nirenberg announced the city's first travel-related case of COVID-19 during a news conference on Friday morning.
He has issued a public health emergency, which restricts gatherings of 500 people or more.
"This is an important step in preventing the spread of the disease," he said.
Two presumptive positive cases also are being reported in Austin.
This is a developing story. Check back with KRIS 6 News for updates.