Police say a suspect is now in custody following the shooting at Los Angeles International Airport.
Multiple people were hit by gunfire, but their condition is unknown, Los Angeles police officer Norma Eisenman said.
She said officers responded to the incident which occurred at 9:30am local time in terminal 3.
The suspect exchanged fire with airport police and was taken into custody. The airport is being swept for precautionary measures and the bomb unit is on scene.
Airport staff evacuated travellers and flights were disrupted nationwide.
Television images showed two people being wheeled away by firefighters. Triage stations to assess any casualties were also seen.
Witness Brian Keech said he heard “about a dozen gunshots” from inside a security gate at the terminal, which has been evacuated.
The Federal Aviation Administration said a “ground stop” was in affect for all flights heading to Los Angeles, meaning planes in any other airport in the country can’t take off for the city.
Other travellers described a chaotic scene as airport security staff evacuated terminals and rushed them outside to the tarmac. Hundreds of people remained gathered outside next to aircraft as authorities investigated what happened.
“People started saying there’s a shooter, there’s a shooter,” said Natalie Morin, who was heading to San Francisco for a graduate school interview.
Emergency crews responded to a multi-patient incident, Fire Department spokesman Brian Humphrey said.
Terminal 3 is home to Virgin America and other airlines.
President Barack Obama has been briefed on the reported shooting.
The White House says the Los Angeles Police Department is leading the response and investigation into the shooting, and administration officials are in touch with federal and local partners.
The White House says it is urging people to listen to authorities and follow directions from first responders on site.
Los Angeles Fire Department spokesman Brian Humphrey called the shooting a multi-patient incident.