LONDON, England -- A Virgin Atlantic plane carrying 357 people from Britain to the United States made an emergency landing at Keflavik airport in Iceland on Saturday following a bomb threat. The plane, flight VS 27, carrying 339 passengers and 18 crew, was evacuated and is now being examined, CNN has learned. Bomb disposal crews were preparing to enter the aircraft, a Boeing 747 en route from Gatwick, England, to Orlando, Florida. The bomb threat is believed to have come about one-and-a-half hours before the emergency landing when a message was found written on a toilet mirror. A spokesman for Virgin Atlantic told CNN that a member of the cabin crew found the message scrawled on the mirror during a routine check. It was never believed the plane was in danger but it made an emergency landing under standard security regulations, the spokesman said. The Virgin Atlantic Boeing 747 took off from London's Gatwick airport at 6 a.m. EST (1100 GMT) bound for Orlando, Fla. It landed safely at Keflavik airport, 30 miles southwest of the capital Reykjavik at 12:26 p.m. EST (1726 GMT). Keflavik Police Commissioner Johann Benediktsson told the Associated Press that the threat was written on a toilet mirror in the plane in soap. It was discovered by the crew and taken very seriously, he added. "It contained the phrase 'all Americans must die' and other anti- American sentiment," he said. Fridthor Eydal, spokesman for the U.S. Naval Base at Keflavik said that dozens of fire engines and support vehicles were scrambled to the airport and ambulances in Reykjavik were placed on standby. "This was a mass casualty situation, but on standby," he said. He said the passengers were taken off the plane into an auxiliary fire station near the terminal building. "The hand luggage is going to be searched and all passengers will be searched," he added.