"Two labourers were declared dead by doctors of 108 ambulance services while two others were rescued," a fire department official said.
The house is located near Devsana Pada ni Pol on Relief Road. The incident took place in the afternoon.
"No one was living in the house. We are finding out who is the owner," police inspector N V Gamit said, adding that the victims might be passing by the old house when it collapsed.
Last August, a girl was killed and six others injured when a three-storey building collapsed in the city. In September, a man died when a part of a three-storey dilapidated building collapsed.