Nepal said on Saturday an error by a "panic-stricken" pilot likely caused the crash of an Everest-bound plane that killed all 19 on board.
The twin-propeller Sita Air plane had just taken off on Friday from Kathmandu and was headed to the town of Lukla, gateway to Mount Everest, when it plunged into the banks of a river near the city's airport around daybreak.
"The pilot's failure to maintain the required radius is a likely cause of the accident," said senior ministry official Suresh Acharya, adding the plane turned too sharply because it had not gained enough altitude.
The Dornier aircraft, which crashed minutes after take-off, was headed for Mount Everest, the world's tallest mountain, killing the 19 people on board, including British and Chinese Everest-bound trekkers.
The plane's right engine burst into flames after being hit by a large bird, causing the aircraft to plummet into the river bank and explode into a huge fireball.
"The preliminary finding of the Civil Aviation Authority notices unusual manoeuvring during the takeoff and the pilot communicated to air traffic control the aircraft was hit by a bird," said Acharya.
"But a plane crash does not occur simply just because its engine was hit by a bird," he said, noting incidents when one engine of a twin-engine aircraft has failed and the plane still is able to land safely.
"The pilot may have been panic-stricken," he added, and "made a steep narrow turn instead of forming a wider radius required to bring the malfunctioning aircraft back to the runway."
Acharya, a member of a government commission due to report on the cause of the crash within three months, said the pilot should have gained more altitude before trying to return to the airport.
The foreigners all arrived in Nepal on Wednesday and had been slated to begin trekking towards Everest Base Camp on Saturday accompanied by local guides on an expedition organised by English firm Explore Worldwide.
Police said the victims were piled up at the cockpit end of the wreckage, the Kathmandu Post reported, indicating they had either failed to fasten their safety belts or took them off before hitting the ground.
The youngest British victim was Ben Ogden, a 27-year-old Oxford University graduate who recently qualified as a solicitor and was a rising star at a London law firm.
His father Andrew was quoted in Britain's Daily Telegraph as saying his son wanted the trip to be "his big adventure" before he "knuckled down to some serious work" and life with his girlfriend of eight years.
Other victims include Timothy Oakes, a 57-year-old secondary school adviser, and his friends Stephen Holding, a 60-year-old retired science teacher.
Building contractor Vincent Kelly, 50, and his brother, property developer Darren, 45, were also killed along with Chris Davey, 52, an electronics engineer, and Ray Eagle, 60, a marathon runner.
It was the sixth fatal crash in Nepal in two years and has raised fresh questions about air safety in the impoverished Himalayan country, home to challenging weather, treacherous landing strips and lax safety standards.
The crashes have claimed the lives of close to 100 people, according to an AFP tally.
British Prime Minister David Cameron on Friday called the crash "a horrific incident" and said: "I feel for the families concerned."
Nepal has a poor road network, meaning many tourists, pilgrims and climbers rely on the country's 16 domestic airlines and 49 airports to reach remote areas.