MYSTERY surrounds the cause of a Nepal air crash that claimed the lives of two Bolton brothers.

Vincent Kelly, aged 50, from Lostock, and Darren Kelly, aged 44, also from Bolton but who lived on the Isle of Whithorn at the time of his death, were among five other British men who were killed when the the plane they were travelling in crashed.

The flight had just left Tribhuvan Airport, Kathmandu, the Nepalese capital, when it got into difficulties on Friday, September 28, 2012, and crashed just one minute and 20 seconds after taking off.

The British passengers were on a trip to Everest base camp organised by an Explore Worldwide Ltd.

Warrington Coroners Court heard that the aircraft, which has been built in 1987, lost power in one of its engines, causing it to drift to the left.

The Dornier 228-202k aircraft stalled while in the air and crashed into the ground at high speed - just 420m south-east of the runway.

The 16 passengers and three crew members died instantly.

A forensic pathologist found all victims died from "blunt force injuries all over the body". They were identified by dental records.

Stuart Hawkins, a senior air crash investigator from Air Accidents Investigation Branch, said a bird hit with the aircraft while it was on the runway, causing a "flash and a bang".

He said: "The bird could explain the flash on CCTV and the bang but not the continued loss of power."

His colleague, Geraint Herbert, a senior inspector of air accidents, said: "It would appear the crew didn't recognise they had a problem.

"There is evidence that one of the engines reduced to 95 per cent of its expected speed at the climbing phase."

He said the engine further decreased while at flight level causing it to stall.

The court heard the fuel flow could have caused the loss of power as the setting was too low but it could not be proved.

The case continues.