An American Airlines flight from San Francisco to New York was grounded for hours and passengers were taken from the plane and questioned after a telephone threat about a possible hijacking, according to law enforcement officials.
The threat eventually was deemed not credible, San Francisco police said in a late-evening statement Thursday.
"The incident is still under investigation, as the individual responsible for the call has not yet been identified," the statement said. "It is a federal crime to make hoax terroristic threats."
American Airlines was in the process of booking passengers from the grounded flight onto alternate flights Thursday evening.
Flight 24 was preparing to take off at 7:30 a.m. when the Transportation Security Administration learned of an alleged telephone threat to the Boeing 767 carrying 163 passengers and 11 crew members.
"TSA was made aware of the alleged threat made via phone against American Airlines flight 24 (SFO-JFK) before take-off," read a TSA statement. "Out of an abundance of caution, TSA requested the plane be moved to a remote location. Passengers were deplaned and interviewed by law enforcement. The aircraft was swept with negative findings and all passengers are safe."
American spokesman Tim Smith told ABC News that the "security threat was phoned in to local police."
According to ABC News San Francisco affiliate KGO, Alameda, Calif., police said they received a call at 9:09 a.m. from a hotel desk clerk saying he received an anonymous call from an individual with an accent threatening the flight.
"It was a verbal threat and that threat involved hijacking the plane," Sgt. Michael Rodriquez of the San Francisco Police Department Airport Division told KGO.
Law enforcement agents surrounded the plane and soon boarded through the back door of the craft, passenger Matthew Hoffman told KGO.
He and other witnesses saw two people taken from the plane in handcuffs.
"They came in rather quickly and went straight to the individual sitting in the other side of the plane and spoke to him a little bit, asked him to stand up, asked him if he had any belongings with him," Hoffman said.
The couple told the Associated Press they believed they were picked at random and later were released without charges.
The San Francisco police statement confirmed that no arrests had been made in the incident.
Fellow passengers weren't so sure the removal of their two fellow passengers was random and reported seeing the pair carrying Pakistani passports, the AP reported.
"It definitely seems like it was racial profiling, based on what they look like physically and the fact they are Pakistani," Michael Anderson, 20, a Yale University sophomore who was heading back to school, told the AP. "It seems like this was a false accusation."
As passengers waited an announcement from the cockpit revealed the threat against the plane, and passengers sat on board the vessel for hours before being bused to an airport terminal, where they and their baggage were rescreened by security personnel, KGO reported.
"We weren't sure there was somebody on the plane or if there was something in the plane, a bomb or something like that," passenger Glenn Dahl told KGO.
ABC News' Scott Mayerowitz and Vic Lee of ABC News' San Francisco affiliate KGO contributed to this report.