The San Antonio International Airport was evacuated this afternoon after a bomb threat was called in.

Police say a caller claimed three parked cars contained bombs. Police dogs detected possible explosives in three vehicles in the basement level of the hourly garage, away from both terminals.

Bomb teams found no explosives in any of the cars or in the long-term lot and the terminals.

Between 1,000 and 2,000 passengers were evacuated onto the tarmac, some waiting nearly two hours in 99-degree heat. They were allowed back inside after police gave the all-clear.

Update at 6:12 p.m. ET: Airline operations have resumed for all flights, an airport spokesman says. Delays should be expected.

Update at 5:47 p.m. ET: The airport entrances have been reopened, KSAT says.

Update at 5:31 p.m. ET: KSAT, citing a police spokesman, says police have found no explosives in three cars in the short-term parking lot.

Bomb teams are now sweeping the long-term lots.

Update at 5:24 p.m. ET: The caller said "that he had left luggage at the airport and the airport was going to blow up," a police spokeswoman tells the Express-News.

Update at 5:12 p.m. ET: Airport authorities are advising all departing passengers to stay away from the airport and check with airlines on the status of their flights.

Update at 5:11 p.m. ET: Bomb technicians continue to examine three cars parked in the basement of the short-term parking garage.

Update at 5:05 p.m. ET: No explosives were found in Terminal A, a fire department spokeswoman tells KSAT-TV.

Update at 4:54 p.m. ET: Departing flights are still being held. Passengers are being bused to a nearby school for temporary shelter.

Update at 4:47 p.m. ET: All arriving flights are landing, airport spokesman Rich Johnson says.

Update at 4:33 p.m. ET: Departing flight operations have been "terminated" for the past hour, an airport spokesman says.

Update at 4:30 p.m. ET: The vehicles are parked in the basement level, more than 300 feet away from the terminals, an airport spokesman says.

Update at 4:25 p.m. ET: At a briefing, San Antonio's police chief said a caller reported three vehicles in the lower level of a parking garage contained explosives. Bomb-sniffing dogs "got three positive hits for possible explosives on three separate vehicles."

The male caller also made "non-specific threats" for both terminals.

Police are trying to trace the call.

Updated at 4:23 p.m. ET: KSAT reports that passengers have been allowed back into the baggage-claim area of Terminal B.

Update at 4:20 p.m. ET: No explosives found in Terminal B, CNN reports.

Update at 4:10 p.m. ET: Citing sources, KENS-TV reports pieces of luggage in a parking garage area are being examined.

KSAT has a live stream.

Airport spokesman Rich Johnson said a "very specific threat" was called in around 2 p.m.

Original post: Both terminals of the San Antonio airport have been evacuated after a bomb threat was called in, according to news reports.

Three bombs were reported in the airport's parking garage about 2:15 p.m. CT (3:15 p.m. ET), a fire department spokeswoman said, the San Antonio Express-News is reporting.

Police have blocked all entrances and exits to the airport, KSAT-TV says.