At least 43 persons were killed when a massive fire ripped through a four-storey building housing illegal manufacturing units in north Delhi’s congested Anaj Mandi area on Sunday morning, in the second deadliest blaze in the national capital.

Almost all deceased were migrant labourers hailing from Bihar and Uttar Pradesh. Police and fire department officials said many of the fatalities occurred due to suffocation as the victims were sleeping when the fire started around 5 am on the second floor of the building, which lacked fire safety clearance and was packed with combustible material like cardboards.

It took over 150 firefighters five hours to douse the blaze. As many as 63 persons were pulled out. While 43, including one minor, died, 16 were injured. Two fire department personnel also suffered injuries, officials said.

Police have arrested the owner, Rehan, and his manager, Furkan, and registered a case under Sections 304 and 285 of the IPC. The case has been transferred to the Crime Branch.

The Delhi Government ordered a magisterial probe into the tragedy, the worst fire accident in the national capital since the 1997 Uphaar cinema blaze that claimed 59 lives. It has sought a report within seven days.

Officials said 30 fire tenders were rushed after the blaze was first reported at 5.22 am in the Anaj Mandi building, which housed manufacturing units for glass items, cardboards, handbags and other goods.