Severe flooding prompted evacuations along the Guadalupe River in Texas on Friday morning after the National Weather Service issued a flash flood warning, the authorities said.

The police in Kerrville, Texas, about 58 miles northwest of San Antonio, said on social media that they were working with the Kerrville Fire Department to evacuate residents, noting that “many roads and streets are flooding in town.”

A Walmart store was being used as “a temporary reunification center” for people who had been displaced by the flooding, the Police Department said. The authorities urged people to stay out of flooded areas and to avoid driving through water. People were also advised not to call 911 for updates.

There were no immediate reports of injuries.

The flash flood warning, which covers southwestern Concho County and southeastern Tom Green County in west-central Texas, is expected to remain in effect until 10:30 a.m., according to the National Weather Service.

Up to four inches of rain have fallen, according to the Weather Service, which said that thunderstorms had brought heavy rain across the area. An additional two inches are possible, the agency said, warning that the rainfall had produced life-threatening flash flooding “of creeks and streams, urban areas, highways, streets and underpasses.”

The Weather Service in San Angelo, Texas, said it had “received multiple reports of flooded roads and homes across Tom Green County.”

“These conditions are life-threatening,” the agency said, warning people stay off the roads if possible.

This is a developing story.