Witnesses said the Dornier aircraft was already on fire when it crashed on the bank of the Manohara River early Friday morning, The Daily Telegraph reported.
The pilot reported a bird hit the plane's right engine, causing a fire, 2 minutes after takeoff from Tribhuvan international airport. The pilot appeared to be trying to turn back, said Ratish Chandra Suman, an airport official.
The plane had not gained enough altitude and turned too sharply, said Suresh Acharya, a senior ministry official.
"The pilot's failure to maintain the required radius is a likely cause of the accident," he said.
Passengers on the plane, which was headed for Lukla, included British and Chinese trekkers bound for Mt. Everest.