The second-floor structure on Camac Street that caught fire on Tuesday morning had a mezzanine floor inside and its stairway had melted by the time firefighters entered, fire department officials said on Wednesday.

Many who entered “What’s in D Name” — a bar-cum restaurant not in operation for months — on the second floor, braving the heat left by the fire after the flames had been contained, wondered whether the structure was legal.

A fire officer said it had central air-conditioning and no openings except for a chimney.

A senior official in the fire and emergency services department said the fire personnel had to punch holes in the walls to let out the smoke.

“There was no window or any ventilation. The smoke was trapped. Our men had to make holes in the walls to create ventilators so the smoke could slowly move out,” the officer said.

For over an hour, a team of over 60 firefighters used water jets from the first floor of an adjoining building, pointing towards the ceiling and the outer walls of the fire-hit structure, to reduce the temperature and contain the fire.

The fire and emergency services department has yet to get the forensic report that could tell the source of the fire and its cause.

A forensic team has collected samples from the spot. “We are waiting for the forensic opinion. Only after that we can tell whether the safety measures in the establishment were adequate or not,” said an officer.

On Tuesday, Rajdeep Chakraborty, who was running the restaurant-cum-bar at the address till a few months ago, told Metro he had “all the required documents and licences”, but those had not been renewed as the place was not operational.

Several fire department officials said the place, though non-functional, was “full of inflammable articles”.

A fire department official who entered the premises recalled his experience of scaling the staircase that led to the second floor.

“We were wearing protective suits, without which we would not have been able to endure the heat. The inside walls of the structure had caught fire. They were all lined with inflammable materials. The place had cubicles that were gutted and a chimney that was burnt,” the official said.

Several LPG cylinders were stored on the same floor. All of them were removed before they could explode, a fireman said. It is not clear if the cylinders were full or empty.

Another official said it was too dark and smoky and it was not apparent if the place had fire extinguishers or overhead water sprinklers.

“Even if there was any, everything was burnt. And whatever fire safety mechanism that floor might have had, it did not work. Else, the fire could have been contained,” he said.

The cause of the fire is yet to be determined. An official said: “The fire often destroys its own source and makes it difficult to ascertain from where it started.”

The police on Wednesday evening said they did not receive any complaint from the fire department till Wednesday evening.