Two or three people were still feared trapped underneath till late evening on Monday, officials said.

Officials added that the five-storied structure crumbled at night and due to space crunch the rescue operations took longer and is still continuing. “The rescue operations involved a series of steps including establishment of communication infrastructures, providing oxygen to those involved, performing search, cutting the concrete slab and then rescuing those who have been trapped,” said an official of the National Disaster team present at the site.

“There isn’t enough space to even clear the debris,” said a disaster management official of the Kolkata Police.

As per the fire department officials and the disaster management team, due to the congested nature of the area, heavy machinery such as JCBs could not be used in the rescue operations making the rescue a manual effort. The ambulance had to be at a distance.

“There are five layers of concrete slab that has fallen on one another. Firstly we are making a hole, cutting that hole using a drilling machine and then people trapped inside are being rescued,” said a disaster management personnel who did not wish to be named. Those involved in the rescue operation complained that narrow lanes made it harder for large rescue vehicles to get access. A fire department official, AK Roy said, “Not necessarily people are trapped at the same location. It’s a L-shaped building…identifying the exact spot and making a hole into the concrete slab to rescue people have been quite a task.”