PHOENIX -- Authorities are continuing to investigate possible threats involving three different Southwest Airlines 737s.
One plane involved in the investigation landed Tuesday night at Sky Harbor International Airport.
A Federal Bureau of Investigation spokesman confirms the Southwest plane in question was taken to an isolation pad away from the terminal where dozens of passengers were removed from the plane one by one to be screened.
The plane, Southwest flight 1184, arrived in Phoenix at 7:30 p.m. after departing from Orange County, California. The plane was bound for Tulsa, Oklahoma.
A source close to the investigation, who spoke on the condition of anonymity because they were not authorized to speak, told me the threats involved three different planes with a connection to Orange County.
The source said two of the planes landed, including the craft at Sky Harbor, and a third flight was canceled as it was set to taxi to the runway at a California airport.
The FBI's Joint Terrorism Task Force is leading the investigation. The Phoenix Police Department also has members on the task force, but a police department spokesperson referred all questions to the FBI.
ABC15 was near the scene at Sky Harbor and watched as FBI agents and other law enforcement entered the plane with bomb sniffing dogs and other tools.
Phoenix police closed down a road near the airport Tuesday night so emergency vehicles could operate in the area.
A similar scene was taking place in California where the other planes had been evacuated and surrounded by law enforcement.