Officials at San Antonio Airport in Texas have evacuated terminals after a "very specific" bomb threat.

Police Chief William McManus said the airport received a call around 2:00 p.m. local time about three possible explosives in three separate vehicles in the lower level of the short-term parking garage. The caller also made "non-specific" threats about the airport itself.

Bomb-sniffing dogs, McManus said, "got positive hits for possible explosives on three separate vehicles." Officials then evacuated the airport at 2:30 p.m. and called in bomb techs to further investigate.

San Antonio Airport posted on its Twitter feed at 2:31 p.m.: "We are evacuating the terminals at this time."

Police, meanwhile, are trying to trace the call.

Airlines have been told that operations at the airport are terminated for the time being and all passengers in the terminals were evacuated for close to an hour before airport officials reopened Terminal B. Terminal A, however, remains closed at this time.

Frank Miller with the San Antonio Airport said about 2,000 passengers were in the airport at the time of the bomb threat. Hundreds of others are on planes on the tarmac that were ordered away from the terminal due to the threat.

Miller cautioned travelers not to come out to the airport until the situation is resolved.