State-run agencies have bought 11.92m tonnes of wheat from farmers so far this season, down 25% on the 15.92m tonnes bought in the same period a year ago
The victims were staying in Daman, a hill resort south of Kathmandu which is known for its panoramic views of the Himalayas.
"They had lit a gas heater to keep the room warm and probably suffocated," police official Hobindra Bogati told Reuters. Seven other tourists in the group were unharmed.