Phoenix Sky Harbor International Airport says two security areas inside Terminal 4 are closed while police investigation as a precaution.
The incident led to the shutdown and evacuation of Terminal 4. Security checkpoints A and D are closed inside the terminal. Meanwhile, police are using a canine to check luggage.
Four Phoenix Metro buses are also parked on the tarmac near American Airlines planes. Video shows police cars on the airport tarmac where planes arrive and depart.
KTVK-TV video shows people in uniform standing around outside the terminal awaiting the all clear.
American Airlines told KNXV-TV it was holding all flights departing for Phoenix.