A BIRD is thought to have caused the Nepalese air disaster that killed 19 passengers and crew after straying into the flight path of the twin-engine passenger jet shortly after take-off.

The Sita Air plane came down minutes after leaving Kathmandu for Lukla before crashing into a river bank and catching fire. Seven British tourists heading for Mount Everest base camp were among the dead.

Footage showed the front section of the plane was on fire when it hit the ground, and it appeared the pilot had attempted to land the aircraft on open ground.

The intensity of the blaze left firefighters unable to immediately reach the area.

Later images showed soldiers and police sifting through the burnt wreckage and charred remains, looking for documents to help identify the victims. One showed a Nepalese soldier holding a British passport.

Tributes were paid to members of the British trekking group who arrived in Nepal on Wednesday for the three-week trip.

Darren Kelly, 45, of Whithorn, Dumfries and Galloway, and his brother Vincent, 50, of Bolton, were part of the trek team along with Raymond Eagle, 58, of Macclesfield, Christopher Davey, 51, of Northampton, Stephen Holding, 60, of Stoke-on-Trent, Benjamin Ogden, 27, of London, and Timothy Oakes, 57, of Warrington;

Mr Oakes's wife Annie Gauny said the mountaineer had always wanted to visit Everest.

She said: "People have got to live and enjoy what they want to do – that is exactly what Tim would want people to do."

Last night Prime Minister David Cameron said: "It is an absolutely horrific incident and obviously I feel for the families concerned.

"We are doing everything we can to inform the next of kin. I know our ambassador in Nepal is on the case and on the spot dealing with it. Obviously we will have to find out exactly what happened."

Thousands of Westerners head to the Himalayas every year to trek in the region around Mount Everest, the world's highest peak.

The crash follows an avalanche on another Nepal peak on Sunday that killed seven foreign climbers and a Nepali guide.

It is also almost a year to the day since another plane crash just south of Kathmandu that killed all 19 people on board, although none were Britons.

James McConnachie, co-author of The Rough Guide To Nepal, said flying in Nepal is "very dangerous indeed".

He said the mountainous terrain and regulation of domestic airlines were "appalling".

Mr McConnachie said: "Regulation is loose and there are bad crashes but in my experience they [the pilots] are mainly brilliant. They have to pull off extraordinary stunts just to get the planes down."

He said the airport in Kathmandu was next to a river that was used as a rubbish dump, which attracted "a lot of birds".

Mr McConnachie said: "It is just a very poor, corrupt country. You cannot trust them [the aircraft] in quite the same way as you can in better-regulated countries."

He said flying conditions were often terrible from mid-morning onwards, with heavy cloud and strong winds.

"There is a Nepalese saying 'Don't fly in clouds in Nepal – clouds have mountains in them'," he said.

Vast investment is made around the world to alleviate the threat of bird strikes, which remain a key cause of air incidents. Recent bird strikes include the US Airways flight from La Guardia to Douglas International which was forced to crash land in the Hudson River in 2009. A year later, a Thomas Cook aircraft survived a "significant" bird strike while trying to land at Manchester Airport.

Philippa Oldham, head of transport at the Institution of Mechanical Engineers, said: "Although it is too early to say definitively what caused this air crash, suggestions have been made that a bird strike caused a catastrophic aircraft failure.

"Ninety-percent of bird strikes occur during take-off or landing of aircraft and the majority of bird strikes lead to little damage of the aircraft. But they can sometimes cause aeroplane failure.

"Aerospace engineers recognise this as a safety issue and are developing computer simulations to model the effects and help mitigate against the impact of bird strikes."