LONDON (AFP) - An EgyptAir plane that made an emergency landing in Britain en route from Cairo to New York after a suspicious note was found on board resumed its journey on Sunday.

British fighter jets escorted the plane to Glasgow Prestwick Airport on Saturday after the discovery of a note threatening to set it on fire, the authorities and eyewitnesses said.

Following a police search of the Boeing 777 plane overnight, it was allowed to continue its journey.

"Officers from Police Scotland have carried out an extensive search of the aircraft resulting in no suspicious items being found," a spokesman for the service said.

"Passengers and crew are now aboard and the aircraft is continuing its flight to New York.

"Officers continue to investigate the circumstances of the incident," he said, without mentioning arrests.

All 326 passengers had been taken off the plane.

The alarm was raised when a passenger, BBC New York producer Nada Tawfik, said she told plane crew that she had found a note in the toilet sink that read: "I'll set this plane on fire."

Ms Tawfik told the broadcaster that the message was scrawled in pencil on a napkin and that it also pinpointed a seat number.

"Either someone has a very bad sense of humour or, you know, it's very scary," she said.

Britain is on high alert as world leaders including United States President Barack Obama and Russian President Vladimir Putin converge on Northern Ireland for the G-8 summit, which begins on Monday.

Britain's Ministry of Defence confirmed that Typhoon aircraft had been scrambled from the Leuchars airbase in Scotland following an incident on board a passenger plane.

Police Scotland said the flight had been diverted following the discovery of a suspicious note on the plane.

Prestwick Airport, on the south-west coast of Scotland, is one of the last places planes can land, if necessary, on the transatlantic route from Europe to North America.