The blaze erupted on the ground floor of the four-storey building on Amroli-Sayan Road where an embroidery factory was operating, divisional fire officer Raju Gamit told PTI.
The garments kept in the factory caught fire and in no time the smoke engulfed the entire building, where the labourers used to stay on the top floor.
The cause of the fire is yet to be ascertained, Gamit said.
As many as 19 labourers were sleeping when the smoke spread to the building’s top floor where there was no ventilation, he said.
Four of the labourers died of asphyxiation as the fire choked the air with smoke, the official said.
Three other persons, who suffered injuries, were referred to a nearby hospital while 12 persons were rescued from the building.
Police and fire department officials have begun investigation into the cause of fire.
“No fire safety equipment was installed in the building, which is eight months old. There was no ventilation in the building. The fire was small but the smoke was dense, which engulfed the entire building within a few seconds, making it difficult for people to escape,” Gamit said.
“Prima facie, there seems to be no sabotage. But, we are investigating from all angles. Two fire fighters were used in the operation and the fire was brought under control in 45 minutes,” he said.