Two Air France flights from the US to Paris have been diverted following a security alert.

Flight AF055 from Washington Dulles and AF065 from Los Angeles were both en-route to Paris Charles de Gaulle when the airline received anonymous threats after take off.

A statement from Air France said: "As a precautionary measure and to conduct all necessary security checks, Air France, applying their safety regulations in force, decided to request the landings of both aircraft."

Intelligence agents are investigating the source of the telephone calls and it was unclear whether the warnings for both flights were from the same person.

FBI agent Todd Palmer told CNN: "Several law enforcement agencies are working to determine the nature of the threats which caused the aircraft to divert".

A passenger on the flight from Dulles, which landed safely in Halifax, Canada, with its 262 passengers, said they were informed the plane was being diverted after two and a half hours of flying.

He said: "Upon landing, one of the flight attendants said it was a security issue that needed to get addressed".

The Los Angeles flight, which had 497 people on board, landed safely in Utah.

American authorities said they found "no credible threat" after searching the Utah plane, passengers and luggage.

Royal Canadian Mounted Police said no evidence of an explosive device had been uncovered during their searches.

Passengers were boarding the planes preparing to complete their journey to Paris.