A Delta Air Lines plane that departed from Los Angeles International Airport bound for Florida was grounded in Texas and evacuated Sunday over a "security concern," an airline spokesman said.

Delta did not release details regarding the nature of the concern on Flight 1061, but multiple Twitter users who were on the flight said a bomb threat had been made, forcing the evacuation of the plane at Dallas-Fort Worth International Airport.

"On the ground in Dallas but still on the plane. Don't really know what's going on other than 'bomb threat,'" tweeted passenger Sarah Chovnick, an NBC sports producer.

Chovnick told NBC4 the pilot notified passengers more than two hours into the flight that the plane needed to be landed immediately because of a security threat.

The plane landed and was taken to a remote area of the airport, where passengers were placed on buses, Chovnick said.

"I’ve never been afraid of flying but this made me a little nervous," Chovnick said.

"Bomb threat on #delta flight from #LAX to #MCO today...we've all been safely evacuated," tweeted another passenger who identified herself as Eva Groves.

The FBI said it was looking into the incident.

"The FBI is aware of recent online threats and is assessing the matter with our law enforcement and airline partners as we do with all threats. Currently, there is no known threat to any aircraft that departed from the Los Angeles area," the agency said in a statement to NBC4.

Flight 1061 left LAX at 10:30 a.m. bound for Orlando, Florida, before being diverted to DFW Airport.

The plane was inspected by authorities, said Delta spokesman Morgan Durrant. The plane and its passengers proceeded to Orlando after being given all-clear about 7:30 p.m.

Also Sunday, two planes, including one from Long Beach, were evacuated on arrival in Seattle after what officials said was a "security concern." Nothing was found on the planes.