Johannesburg - The Natref jet fuel storage and supply system to Johannesburg's OR Tambo International Airport was being flushed on Friday following contamination, Sasol said."An investigation into the cause of the contamination is underway and as soon as it is clear how this happened, appropriate actions will be taken," company spokesperson Jacqui O'Sullivan said.A delivery of around seven million litres of jet fuel from the National Petroleum Refineries of SA to the Airports Company of SA (Acsa) had been declared off-specification and therefore segregated.Sasol and the Total Oil and Petroleum Company are joint venture partners in the facility, which pumps the fuel to the airport.O'Sullivan said discussions were underway to minimise any potential impact on the airport."Among the options already activated is an agreement with airlines to take up additional fuel at alternate sites in the country, thereby reducing demand at OR Tambo Airport," she explained.Sasol had also asked other service providers to provide short-term support pending the resumption of normal pumping activities at Natref. Transnet Freight Rail had made additional capacity available from the coast.It was anticipated the Natref facility would be cleared to resume normal pumping of jet fuel to the airport over the weekend."The resolution of this matter is our priority and we will restore normal operations as quickly as possible," she said.Earlier, Acsa spokesperson Solomon Makgale said the airport was operating normally."People must come to the airport, it is running."On Thursday he said Acsa had been advised by the fuel consortium that the fuel line between Natref in Sasolburg and the airport had been contaminated with "off-specification Jet A-1" fuel.Therefore, instead of having its usual four-day supply the company was left with enough for 1.6 days.It appeared the contamination was detected before the fuel got into aircraft.The airport normally received about three million litres of fuel a day, through the Natref pipeline.Details on the cost of the contamination, and whether the fuel could be recycled or reused, were not immediately available.The airport served around 17 million domestic and international passengers a year.