A United Airlines commuter flight carrying 47 people from San Francisco to San Antonio was diverted to Phoenix on Thursday after an undisclosed threat was made against the plane, authorities said.
After making the unscheduled landing at about 4:45 p.m. local time, the plane was sent to an isolated portion of the airport, where its passengers were evacuated while local police investigated, authorities said.
The threat, which came on Halloween, was found on the plane, said Sergeant Steve Martos, a spokesman for the Phoenix police department. He did not release further details.
An initial search of the aircraft by investigators and police dogs did not turn up any dangerous materials, Martos said. But he said further investigation by his department's bomb squad was still ongoing.
The FBI will investigate the threat, Martos added.
Julie Rodriguez, a spokeswoman for Phoenix Sky Harbor airport, said that no flight delays or roadway restrictions were expected as a result of the unscheduled landing or the investigation.
(Reporting by Sharon Bernstein; Editing by Paul Simao)