The engines of a jet that crash-landed at Heathrow Airport had no mechanical defects, investigators have said.
The AAIB said the engines were running at the time of the crash
The Air Accidents Investigation Branch (AAIB) added the black box data recorder showed nothing wrong with the major aircraft systems.
But there was some damage to the fuel pumps, and some small items of debris were found in the fuel tanks.
All 136 passengers and 16 crew on the British Airways flight from Beijing survived the incident on 17 January.
Not giving any cause of the accident, the AAIB said it was carrying out a full examination and analysis of the entire Boeing 777 aircraft and engine fuel system.
It added it had ruled out ice, water and bird ingestion into the engines or contamination of fuel tanks.
With the cockpit crew unable to get the required thrust from the engines as the plane approached Heathrow, the aircraft had come down on the grass "some 1,000ft short of the paved runway surface and just inside the airfield boundary fence", the report on Monday said.
As the plane skidded across the grass and on to the end of the runway, the underside of the aircraft collapsed.
The report said a significant amount of fuel had escaped the aircraft on landing but had not caught fire.
All occupants were safely evacuated, with one passenger suffering a broken leg and eight others receiving minor injuries. Four crew were slightly hurt.
The AAIB did make one safety recommendation. This concerned the order in which the cockpit crew went through the evacuation checklist procedures.
Boeing raised no technical objection to BA introducing a save-time checklist sequence, but the report said this led to the loss of fuel from the aircraft.
The AAIB added: "This was not causal to the accident but could have had serious consequences in the event of a fire during the evacuation."
The AAIB recommended that Boeing tell 777 operators to do the evacuation checklist in the right order. Boeing had accepted this.