"There was very much heat and then the fire began. They were very close to the airport. After two or three minutes it crashed," the official was quoted as saying.
The dead include the crew - a pilot, a co-pilot and an air hostess.
The Dornier Aircraft 9N-AHA of Sita Air crashed at 6.10 am just a kilometre away from the Tribhuvan International Airport in Kathmandu, killing all 19 people onboard.