The doomed may have had an emergency-power generator operating when it crashed, investigators believe. The suggestion raises questions about whether the engine of the was operating properly during take-off.

The plane crashed in a residential area only seconds after leaving the . The preliminary finding, reported by the Wall Street Journal, comes as at least 270 people died in the crash, including 241 out of the 242 people on the plane and some on the ground in the Indian city.

The emergency system is known as a ram air turbine, which deploys automatically in flight if both engines have failed or if all three hydraulic system pressures are low, according to an instruction manual for Boeing 787 planes.

The back up system is normally activated if a pilot thinks that both engines have failed. Engine failure can be caused by a numebr of factors, such as bird strikes or fuel problems.

Anthony Brickhouse, a US-based aerospace safety consultant, told the that twin engine failures were extremely rare.

Flight AI171 issued a Mayday call moments after taking off from Ahmedabad's Sardar Vallabhbhai Patel international airport on June 12.

It reached only 650 feet before crashing into a medical college complex, erupting into a fireball. Only one person on board the flight survived the horrific crash, with at least 29 people on the ground also killed.

Inidan offficials said on Tuesday they had matched the DNA of 135 victims and returned 101 bodies to relatives, though they said five of those individuals had not been listed on the flight manifest.

Many victims were burned beyond recognition, making it extremely difficult for rescue teams to identify the crash victims.

Dr Rakesh Joshi, medical superintendent at Ahmedabad civil hospital, said: "135 DNA samples have been matched, and 101 bodies have already been handed over to the respective families. Of these 101 deceased, five were not on board the flight."

He added he hoped DNA profiling would be completed by Wednesday.

Brit Vishwash Kumar Ramesh, 40, was the sole survivor and described the horrific moments of the crash as it unfolded.

"Right in front of my eyes, I saw air hostesses, uncles, aunties dying," he said.

India's Aircraft Accident Investigation Bureau is leading the inquiry, supported by UK and US safety agencies.

Investigators are examining various possible causes, from thrust-and-flap settings to fact that the landing gear did not appear to have been retracted.