Europe's air safety authority has ordered airlines to conduct more tests on the type of Rolls-Royce engine that failed in an Airbus A380 superjumbo.
The European Aviation Safety Agency said in a new "emergency airworthiness directive" posted on its website that airlines using the Trent 900 engines should conduct "repetitive inspections" on the engines.
Airlines should be checking several parts of the engines, including the oil service tubes, to ensure there is no "abnormal" leakage, the agency said.
If any such leaks are found, the airlines are banned from using the engines.
It follows the mid-air disintegration of a Trent 900 engine on a Qantas A380 superjumbo on November 4 as it took off from Singapore, leaving large chunks of debris scattered across an Indonesian island it was flying over at the time. The plane made an emergency landing without any injuries back at Singapore.
The European agency said analysis of the early stages of the investigation into the Qantas incident "shows that an oil fire" in part of the engine "may have caused the failure of the Intermediate Pressure Turbine Disc".
It went on: "This condition, if not detected, could ultimately result in uncontained engine failure potentially leading to damage to the airplane and hazards to persons or property on the ground."
Qantas has grounded its six A380s fitted with Trent 900 engines while checks are carried out. Singapore Airlines has grounded three of its 11 A380s.
Lufthansa, the other airline using that plane-engine combination, said on Wednesday that its planes were all flying after safety checks were completed.