The building, which belonged to a retired government official, Dhruv Kumar, collapsed at 9:45 am in the morning.
No deaths or injuries have been reported yet.
The owner of the building and a labourer is suspected to be stuck under the debris.
"Three fire tenders and a team of the DDMA, and the local police are at the spot," DCP South East Romil Baniya said.
The building was reportedly under construction. (ANI)