The rescue department estimates the size of the leak at 14,000 litres of light fuel.
Some of the oil has ended up in the rain water drainage system, through which it has reached outskirts of the airport.
The leak was detected on Wednesday but the rescue department said the damage had largely happened earlier.
The point of leak, according to the rescue department, is a maintenance building located at the airport’s second terminal which serves as a heating centre and houses backup generators.
