Out of the two labourers injured in the blaze, the condition of one, a 28-year-old resident of Ushpara village in South 24 Parganas district, was stated to be critical, the police said.
The other labourer is was out of danger, the police added. The fire is totally under control. At present, there are no flames and only smoke is visible. Four fire tenders are working to cool off the place and douse the pocket fires, a senior police officer said.
The fire could have been caused due to a short circuit, he said adding forensic experts will conduct an examination of the building.
(With inputs from agencies.)