CHICAGO — About 1,000 people were evacuated from the airport in the US city of San Antonio on Wednesday after the Texas facility received a "credible" bomb threat by telephone, a spokesman said.

Passengers and staff were escorted out onto the sweltering tarmac while a bomb squad swept the terminal buildings, but flights were not diverted.

"Inbound planes are being allowed to land," airport spokesman Rich Johnson told CNN.

"They're just being held out on our tarmac area away from the terminal facilities at this time."

Planes already at the airport were either cleared to take off or were backed away from the building as a precaution because the threat was considered credible, Johnson said.

"It was called in specifically to our airport," he explained. "There were specific locations as well as specific numbers that were given to the people who answered the phone."

The threat was called in at 2:35 pm (1935 GMT), and one of the airport's two terminals was cleared within the hour, Johnson said in an e-mail to AFP.

The airport handles an average of 260 domestic and international flights and 14,000 to 15,000 passengers a day.