An air base in the US state of Arizona has been placed under partial lockdown, as officials investigate a report of an armed individual.
Davis-Monthan Air Force Base officials said that traffic had been limited around the facility.
They denied a local media report that shots had been fired or that someone had been injured.
Two elementary schools are on the base, said Senior Airman Timothy Dunaway, but the students were safe.
The lockdown was prompted by reports of a person with something like a weapon, Tech Sgt Russ Martin told the Associated Press news agency.
"So the base is going into crisis action mode. We're just locking down the base for the safety and security of the people on Davis-Monthan," he added.
He confirmed reports of an ambulance being directed to the base, but said it was for a pregnant woman who had gone into labour.
Earlier, local television station KVOA reported via its Twitter account that the Tucson Fire Department was responding to the base "for possible patient with multiple gun-shot-wounds".
But a short time later an unnamed base spokesman said: "No shots have been fired and no-one has been hurt.
"Reports of suspicious activity have caused DM [Davis-Monthan] officials to declare a higher state of security. We are conducting investigations."