The engines on the British Airways Boeing 777 that crash-landed at Heathrow airport last month showed "no evidence" of a mechanical defect.
Nor did a take-in ice or a birdstrike, according to an accident investigation report.
The special bulletin from the Air Accidents Investigation Branch (AAIB), said investigations were now "underway to attempt to replicate the damage seen to the engine high-pressure fuel pumps and to match this to the data recorded on the accident flight".
The AAIB also said that a comprehensive examination and analysis was to be conducted on the entire aircraft and engine fuel system.
This examination would include the "modelling of fuel flows taking account of the environmental and aerodynamic effects".
Last month the AAIB said the engines on the British Airways jet were running when it came down on January 17.
All 136 passengers and 16 crew on the flight from Beijing survived the incident.
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