A United flight was grounded after a passenger found a bomb threat note in the bathroom: reports

• A United Airlines flight was grounded for several hours in Vermont on Sunday.
• A local NBC affiliate obtained audio of the plane's pilot discussing an apparent bomb threat.

A United Airlines flight was grounded for more than two hours in Burlington, Vermont, on Sunday after a passenger discovered a bomb threat in the plane's bathroom, according to authorities and reports.

Approximately 20 minutes before flight 3613 out of Newark, New Jersey, was scheduled to land in Burlington, flight crew notified air traffic control of a threat onboard, a spokesperson for the airport said in a Sunday evening news conference.

Several law enforcement agencies responded to the incident, including the Vermont National Guard fire and rescue department, South Burlington Police, the Department of Homeland Security, the FBI, and Burlington Police Department, Nic Longo, director of aviation for Burlington International Airport said Sunday.

Authorities found nothing "unusual or suspicious" after searching the plane, according to officials, but a federal investigation into the incident is ongoing.

The approximately 65 passengers onboard were finally allowed to deplane around 6:45 p.m. — more than two hours after the flight was originally scheduled to land, at which time they were made aware of the situation, officials said. The Burlington airport was closed during the search and reopened around 7:30 p.m. local time.

Burlington Police Chief Jon Murray declined to answer questions about the specific nature of the threat, citing an ongoing investigation, but confirmed during the Sunday press conference that the Vermont State Police bomb squad was on the scene.

Local news station WPTZ obtained audio of the pilot discussing the situation with air traffic control.

"A flight attendant just came up and said that a passenger found a note in the aft lav that said there was a bomb on board," the pilot can be heard saying.

Passengers told the outlet that K-9 units also swept the plane while they were still onboard.

"It was scary," passenger Melissa Jones told WTPZ. "I had to stay calm because of my kids."

No injuries were reported and authorities said there was no reason to believe the incident was anything but isolated.

A spokesperson for United referred Insider to Republic Airways, which was operating the regional flight. A representative for Republic Airways said the aircraft was taxied to a remote location at the Burlington airport and a "precautionary security sweep" of the plane was performed with no findings.