Morrisville, N.C. — The FBI early Saturday said a misunderstanding apparently sparked an incident on a flight from Florida that Raleigh-Durham International Airport officials initially classified as a possible terrorist incident.

FBI agents determined that a "misperception" caused the alert and said there was never any threat to passengers or crew members.

American Eagle Flight 4518 left from Jacksonville, Fla., at 7:10 p.m. for Raleigh. "Approximately 30 minutes prior to landing, a flight attendant observed suspicious activity by two of the passengers and reported this activity accordingly," the FBI said in a statement.

Dozens of law-enforcement and emergency personnel met the plane at a remote part of the airfield around 8:20 p.m. Three crew members and 27 passengers were kept on the plane for more than an hour, until RDU police, FBI agents and airport emergency crews evacuated them on movable stairs around 9:50 p.m.

RDU police bused passengers to a building where they were questioned, and explosives teams checked the bags form the flight.

Early reports said the FBI arrested two passengers, but hours later, the FBI said it had arrested no one and was closing the case.

"Subsequent investigation, including interviews with those aboard the aircraft and a search of the airplane, has determined there was never any apparent threat or danger to the passengers or crew, and the observed activity was apparently misperceived," agents added.

Around 12:30 a.m. Saturday, four hours after their plane landed, passengers were taken to terminal C, where they collected their bags, which had been checked by bomb-disposal experts, and went on their way.

RDU commercial operations proceeded normally during the incident, with both main runways open.

The reported "disturbance" on the plane was initially classified as a terrorist threat as a precaution, according to RDU Spokeswoman Colleen Fischvogt.

Flight 4518 had been scheduled to arrive at Gate C26.The plane was an Embraer ERJ-145, a regional twin-engine jet, according to its schedule information.