Burlington International Airport was closed for three hours Sunday after air traffic controllers were notified of a threat to an inbound United Airlines flight.

United Flight 3613 left Newark, New Jersey, at 3:14 p.m. and was scheduled to land at about 4:30 p.m. However, BTV Aviation Director Nic Longo said that about 20 minutes before its arrival, the United flight crew notified air traffic control of a threat to the aircraft.

The massive response included a Vermont State Police bomb squad, officers from the Burlington and South Burlington police departments, the Department of Homeland Security and the FBI.

At an airport briefing, Longo did not discuss the nature of the threat, but said nothing unusual or suspicious was found on the plane. No injuries were reported.

“The airport followed our airport emergency procedures and responded to the event,” Longo said. “Upon landing, the aircraft was directed to a specific location.”

About 65 passengers were on board the flight. They were remained on the plane for about two hours after landing. They were evacuated while a police K-9 crew searched the aircraft.

The airport re-opened at about 7:30 p.m.

“What we have here is a safe group of people,” Acting Burlington Police Chief Jon Murad said. “We have a safe plane, we have a safe airport, we have procedures that were followed and we have a successful outcome.”