A day after a massive blaze engulfed a three-storey commercial building in Lucknow's Aliganj, killing 15 people and injuring several others, authorities have sealed the premises, registered an FIR and launched a probe into the matter.The three-storey building had come up on a plot originally meant for residential use. (PTI)The victims were mostly students and young professionals associated with an animation training centre and gaming zone located inside the building in Purania Sector-D. The blaze occurred around 2 pm on Monday, with eyewitness accounts and visuals from the scene showing panic as occupants of the building made desperate attempts to escape.Some were seen rappelling down power lines, while others jumped off as firefighters worked to bring the blaze under control. President Droupadi Murmu and Prime Minister Narendra Modi expressed grief over the loss of lives.Also Read | Lucknow tragedy: Height loophole left building exempt from fire checksPM Modi also announced an ex gratia of ₹2 lakh for the next of kin of each deceased and ₹50,000 for those injured. Meanwhile, Uttar Pradesh chief minister Yogi Adityanath announced the cancellation of the remainder of his scheduled visits to Aligarh and Hathras.No fire NOC, biometric lock delayed escape: What we know• No fire NOC: The three-storey building had come up on a plot originally meant for residential use and had not obtained a fire NOC (no objection certificate), according to an earlier HT report. Under building bylaws, such certificates are required for buildings above 15 metres, but this complex was less than that height, Ankush Mittal, chief fire officer, Lucknow, said. He added, “The operators had not approached us for the NoC.”• Premises sealed: Following the blaze, the Lucknow Police sealed the building in the Aliganj Police Station area, further prohibiting the entry of the general public. The forensic and fire departments are preparing to collect evidence from the site, ANI news agency reported.• FIR filed, SIT probe launched: The police registered an FIR after the incident under Sections 110, 105, 125 and 3(5) of Bharatiya Nyaya Sanhita (BNS), along with Sections 6 and 10 of the Uttar Pradesh Fire Service Act. Meanwhile, the Uttar Pradesh government constituted a two-member Special Investigation Team (SIT) to probe the incident.• Biometric lock delayed escape: Firefighters battling through the blaze were allegedly unable to enter through the building’s only access route, according to an earlier HT report. Allegations have emerged regarding a biometric locking system at the entrance, which may have delayed the escape of those who were trapped inside the building.• Lapses in monitoring by LDA - The blaze exposed glaring lapses in monitoring and enforcement by the LDA, with questions being raised over the functioning of a residential plot as a commercial complex for years. The 1,992 sq ft property was bought in 2013 by brothers Virendra and Surendra and approved in 2014 only for residential use, according to official records.Demolition notice to building, cause of fire: What remains unknown• Demolition decision reversed: The three-storey building in Aliganj was issued a demolition order in 2016 over unauthorised construction. The building was originally allotted to Vijay Kumar, son of Rameshwar Sahay, on July 11, 1980, under a hire-purchase scheme through a lottery system, PTI news agency reported.In 2005, the property was registered in the names of Vijay Kumar and his wife, Usha, through a sale deed, and was later sold to Virendra Pratap Shukla and Surendra Pratap Shukla in 2013. While the building was approved for residential use, unauthorised construction was subsequently detected on the premises. After an inquiry, a demolition order against the unauthorised construction was issued in May 2016, but was reversed within two months. This has raised questions about the circumstances in which the reversal occurred.• Uncertainty over cause: Officials have said the fire was likely triggered by a short circuit in an LED billboard installed in the basement. However, Uttar Pradesh development and energy minister told PTI that the blaze may have started in the building’s AC duct.Meanwhile, UP deputy chief minister Brajesh Pathak said a high-level inquiry had been ordered into the incident to ascertain the cause of the fire and determine how it occurred.