Investigators probing the crash in January of a British Airways jet at Heathrow airport are focusing on problems in fuel systems both within the aircraft and inside the engines themselves as the possible cause.

The 150-tonne Boeing 777 suffered a catastrophic loss of engine power in the final seconds of its flight from Beijing. It crashed just inside the airport perimeter fence, 1,000ft short of the southern runway.

The impact tore off the right landing gear and pushed the left landing gear up through the wing as the aircraft skidded across the grass to the runway’s end. The 136 passengers and 16 crew escaped with only one serious and eight minor injuries. The crash was the first by a 777.

The Air Accidents Investigation Branch of the UK transport department said in its latest report, published on Monday, there was evidence both engines had been affected by low fuel pressure at the inlets to high pressure pumps. It said it suspected restrictions in the fuel system between the aircraft fuel tanks and each of the en0gine’s high pressure pumps had meant reduced fuel flow to the engines.

During the flight the BA jet had passed through a region of particularly cold air between the Ural mountains and eastern Scandinavia, with ambient temperatures as low as –76C, the AAIB report said.

An analysis of the jet fuel on board showed it was of good quality, however.

There was no evidence of contamination or excessive water that could have been affected by the very low temperatures.

The minimum recorded fuel temperature during the flight was –34C. The fuel on board had a measured fuel freezing temperature of –57C.

The AAIB said full-scale engine testing had been conducted by Rolls-Royce in Derby and fuel system testing was still under way by Boeing in Seattle.

The primary challenge for the Boeing tests was to reproduce the environmental conditions and fuel effects experienced on the flight over Siberia at altitudes of up to 40,000ft.

The AAIB said the tests at Boeing and Rolls-Royce were aimed at understanding the potential for the development of restrictions that could have limited the flow of fuel. It had also started work on trying to develop an improved understanding of the dynamics of the fuel as it flowed from the fuel tank to the engine.

No operational changes as a result of the crash have to date been recommended to airlines flying 777s.

An extensive examination of the aircraft had revealed no evidence so far of malfunction of any aircraft or engine control system, the report said.

There was no evidence of the aircraft being affected by the wake turbulence of another jet nor any evidence of a bird strike nor of icing in the core engine.