(AP) -- A plane from Cairo bound for New York was diverted by fighter jets to an emergency landing in the U.K. after a passenger discovered a letter threatening the aircraft, officials said Saturday.

Police said late Saturday there had been no arrests, and that authorities are working to ascertain who wrote the note in a lavatory which forced Flight 985 -- carrying around 300 passengers en route to John F. Kennedy Airport -- to make an emergency landing at Glasgow's Prestwick Airport.

British Typhoon fighter jets escorted the plane to Glasgow's Prestwick Airport, where the flight was met by a heavy police presence. It stayed there for several hours before passengers were able to disembark, at which point officers searched the plane.

The BBC said one of its producers, Nada Tawfik, had discovered the note, written in pencil on a napkin, with the words "I'll set this plane on fire" and what appeared to be a seat number written on it. She said that after discovering the note by the lavatory sink, she alerted cabin crew who then locked the toilet.

"It almost looked like a child's handwriting or someone who has very sloppy handwriting, but it was very alarming especially these days when everyone is so concerned about safety on flights" she told the BBC, saying she told the stewardesses she wasn't sure if the note was a prank or not. "Either someone has a very bad sense of humor or, you know, it's very scary."

Det. Superintendent Alan Crawford said there have been no arrests, and that police are working to determine where the note came from, who put it on the plane and under what circumstances.

"This note, whatever narrative it contained, we have to treat it seriously and maintain the safety of passengers and crew," Crawford said. "Whether it is a prank or not this will be investigated thoroughly to establish the circumstances. We could never write something off as a prank without investigating."

Arrangements for onward travel will be made once all passengers have been interviewed, police said.