The building on Canning Street, parts of which collapsed on Thursday. Picture by Pradip Sanyal

A four-storeyed building, let out to firms and a family, on Canning Street partially collapsed on Thursday morning. There were no casualties as the offices were closed and members of the family residing there managed to escape.

The building on a 10-cottah plot at 21D, Canning Street houses 17 offices and godowns. Parts of the first and the second floors collapsed at 10.45 am, prompting mayor Subrata Mukherjee to seal the building under Section 411 of the civic building rules.

?Unsafe portions of the building will be demolished,? said Swapan Samaddar, mayor-in-council member (buildings). The demolition will start on Friday morning.

Director-general (buildings) Ashok Roychowdhury said the century-old building was in a dilapidated state, but its condition couldn?t be ascertained from outside because of a fresh coat of paint. ?Thanks to the paint, nobody could guess that portions of it would collapse like a pack of cards.?

A few years ago, the civic body had sent a notice to the property owner, stating that the building was unsafe and that it required immediate repairs, Samaddar informed.

Two days ago, there were some indications that the building might collapse. ?Some bricks on the rear portion had fallen off. We had informed the authorities about it, but no action was taken,? said Kunal Bangur, who runs an office on the premises.

Shocked tenants are thanking their stars that the tragedy had struck on a holiday. They alleged that the third floor of the building was constructed illegally a decade ago.

?We were preparing food when we heard a thud,? said Jigar Dattani, a Class XII student who stays in the building with his parents and grandmother. The family has been staying there since 1944. ?Hearing the shouts of people outside, we hurried out,? he recounted. Jigar, his parents and 70-year-old grandmother climbed down the stairs as the concrete was crumbling down all around them.

According to Roychowdury, there are over 1,200 unsafe buildings in the city, mostly in Chitpore, Nimtala, Sovabazar, Ahiritola, Beleghata, Jorasanko and Burrabazar.