The construction of the four-storey building in Vidyasagar Colony that is now leaning dangerously started around 2009-10.

The recent repairs and “lifting” with the help of joists started a couple of months ago, said Mitali Banerjee, the local councillor (Ward 99) of the Kolkata Municipal Corporation (KMC).

“Since the building was constructed without a permit from the civic body, it is difficult to say immediately whether any soil test was done before the construction,” a civic official said.

Residents said on Tuesday the plot where the building stands used to be a pond.

The KMC has yet to confirm whether the water body was filled illegally to raise the structure or if the nature of the plot was converted legally before the construction started.

Architects and engineers not associated with the KMC said a soil test is necessary to know the load-bearing capacity of the plot on which a structure would come up.

“Our records do not show any building permit was issued for the structure,” a KMC official said.

“The repairs that started a few months ago were being done without any permission from the civic body. The KMC building rules say permission has to be sought from the civic body for any major repairs,” the official said.

“Preliminary reports suggest the building had tilted and the repairs were being done to make it straight again. This is a major repair and it cannot be done without the KMC’s permission.”

Banerjee, the local councillor, said residents of the building told her that the developer had contacted them after an illegal building in Garden Reach collapsed last year. “The developer told them the building had tilted and he wanted to undertake repairs to fix the error,” she said.

Questions have been raised about the KMC’s role in the episode. The KMC had promised to set up a mechanism to identify illegal construction.

Many in the neighbourhood asked how the repairs could have escaped the attention of the councillor or her aides.

“The developer had put up a cover outside the building and it was impossible to know what repairs were being done,” Banerjee said.

A senior KMC official said: “We are inquiring into all aspects. We are now focusing on pulling down the structure safely.”

An architect not associated with the KMC said the structure’s foundation must be examined and a soil test would help determine the cause of the collapse.