Authorities say a Southwest Airlines plane finishing a flight from Baltimore to Denver was parked in a remote area at Denver International Airport Saturday evening because of an unspecified security threat.

Airport spokesman Heath Montgomery tells the Denver Post (http://dpo.st/1KFB4Wc) that the passengers were being shuttled to the main terminal by bus.

The Post reports that authorities were made aware of the threat about 5:15 p.m. and the plane landed safely at the airport at 6:36 p.m.

Montgomery identified the plane as Southwest Flight 3456.

He deferred other questions from the newspaper to the FBI, which is investigating along with Denver police and the Transportation Security Administration.