The Civil Aviation Department has urged its Indonesian counterpart to conduct an extensive review into the aircraft refuelling system at Surabaya airport, saying contaminated fuel caused the April 13 emergency landing of a Cathay Pacific A330 at Hong Kong International Airport.

Releasing its preliminary report into the incident today, the department said suspicious "spheres" were found in the plane's fuel. The particles caused numerous fuel components in both engines to seize, resulting in the emergency landing.

The exact source and nature of the spheres is being examined. The investigation has so far found extension work had recently been done to the hydrant refuelling circuit the aircraft used before departing Juanda International Airport. But the re-commissioning procedures of the extension work did not comply with aviation fuel industry guidelines.

The department urged the National Transportation Safety Committee of Indonesia to conduct an extensive review of the re-commissioning procedures, using qualified and experienced personnel, to ensure the system complies with industry standards.