Civic authorities had last week "surveyed" the four-storey building housing illegal manufacturing units, where 43 people were killed in a massive fire on Sunday, but the upper floors were found to be locked due to which the entire structure could not be inspected, according to official sources.
Officials were to visit the building again to survey the upper floors and accordingly issue a show-cause notice, a source said.
A preliminary probe by authorities suggested that a short-circuit triggered the fire which started on the building's second floor.
"The building was surveyed last week by civic authorities, but upper floors were found locked so the entire building could not be surveyed," an official source claimed.
The building is under Delhi Laws (Special Provisions) Act, 2006 which protects unauthorised construction from being sealed.
"The unit would have been closed by authorities if not found to be permissible as a household unit under provisions of the Master Plan of Delhi," the source said.
The building, spanning an area of 600 sq yards, had just one door. Fire department personnel had to cut window grills and metal meshes to enter to rescue trapped people, the Delhi Fire Services officials said.
Only one fire tender could be sent at a time through the narrow congested lanes, he said.
It took over 150 fire fighters nearly five hours to douse the blaze. As many as 63 people were pulled out from the building. While 43, including one minor, died, 16 were injured. Two fire department personnel were hurt while carrying out the rescue work, officials said.
The massive fire ripped through the building housing illegal manufacturing units in north Delhi''s crammed Anaj Mandi area on Sunday morning, in the deadliest blaze in the national capital since the Uphaar tragedy in 1997 in which 59 people were killed and over 100 injured.
Almost all the deceased in the Anaj Mandi fire were migrant labourers hailing from Bihar and Uttar Pradesh.
Police and fire department officials said many of the fatalities occurred due to suffocation as people were sleeping when the fire started at around 5 am on the second floor of the building that did not have fire safety clearance and was packed with combustible material like cardboards, plastic sheets and rexine.
The Supreme Court in its order in the MC Mehta Vs Union of India and others case had observed that under the Master Plan of Delhi, non-residential activities in residential premises are permitted only under certain conditions as laid down in the Master Plan.