Security sources as saying the blast appeared to be at a structure used to store fuel.
Egypt's civil aviation minister Younis al-Masry concurred that the blast had occurred at fuel tanks outside the airport's perimeter.He said air movement at the airport had been "unaffected".
An Egyptian army spokesman later said the explosion was the result of high temperatures near the tanks.
The blast could be heard across large parts of the city.
The incident will further heighten tensions in the country, with the airport the scene of a terror attack which claimed the lives of all 224 passengers on board Metrojet Flight 9268 in 2015, which an investigation suggested was the result of a bomb smuggled on board.
Egyptian state television is reporting that a fire raging as a result of the explosion had been brought under control, and that the tanks belonged to a private company, which was not identified.
Television pictures also showed ambulances racing towards the scene.
There is no confirmation so far of any casualties.
One Twitter user, Matthew Keidas, has said: "This guy says a worker at the airport said it was an explosion at the fuel depot in Cairo airport.
"Hopefully everyone is alright and it's an accident rather than foul play."
More to follow...
