Two passengers on a Pakistan Airlines plane Friday that was escorted by U.K. fighter jets for an emergency landing at a London Airport have been arrested on charges related to the incident.

It’s unclear exactly what happened on the Manchester-bound plane, but early indications are that the incident was not terror-related. The U.K. is on edge following the near beheading of a soldier in London earlier this week that was allegedly perpetrated by radical Islamists.

Pakistan Airlines Flight 209, a Boeing 777, took off from Lahore and shortly afterward U.K. fighter jets scrambled and escorted it to Stansted Airport, near London, where it landed around 2:10 p.m. local time. The two passengers were then arrested on charges of suspicion of endangering an aircraft, according to CNN.

Essex police, which has jurisdiction over Stansted Airport, told Reuters that an “incident” occurred on the flight but did not elaborate.

"An incident has occurred on an aircraft," the police said. "Police and partners are responding. A further update will be released as soon as possible."

The Ministry of Defence also declined to go into detail about what led to the scrambling of the fighter jets and the plane’s subsequent diversion.

"Typhoon aircraft from RAF Coningsby were launched today to investigate an incident involving a civilian aircraft within U.K. airspace; further details will be provided when known," the Ministry of Defense said in a statement. The Royal Air Force base is situated in central England.

According to Russia Today, the plane was diverted for “security reasons.”

A range of possibilities exist for the diversion, from a sick passenger to a bomb threat.