A Southwest flight declared an emergency and returned to the airport gate late Sunday night because of a "passenger disturbance," said airport police.

Following a three-hour delay, Flight 2010 was on the taxiway at Los Angeles International Airport when a woman reclined her seat and the man behind her started choking her, a passenger on the flight told NBC.

"At 10:43 p.m., we received a call about a passenger disturbance on the Southwest flight," Rob Pedregon, public information officer for Los Angeles Airport Police told Mashable. "The pilot diverted back to the gate, but the plane never took off. It was on the taxiway."

"Because of a rapidly escalating situation involving passengers who were not traveling together," the captain declared an emergency, Southwest Airlines said in a statement. The plane was back at LAX about 13 minutes after left.

The airline confirmed the physical altercation happened onboard.

Airport police met the aircraft at the gate and removed the passenger. The FBI took over and launched an investigation, airport officials told Mashable.

A passenger on the flight posted a photo of the scene on Instagram: "A man strangled a woman because she tilted her seat back," she wrote in German.

The man “started choking her. She shouted for help and the crew came to see what happened. The man stayed very calm during the whole situation,” the passenger told NBC.

"An individual was detained for questioning following the return of a SW aircraft to LAX based on allegations of an assault involving a fellow passenger,” FBI spokeswoman Laura Eimillier told NBC. “No arrest has been made at this time and the investigation is continuing.”

The remaining 136 passengers switched planes and, due to an air traffic control delay, reached San Francisco at 1:43 a.m., about five hours after their scheduled arrival.