The blaze was the worst in Delhi since 59 movie-goers died in a cinema in 1997, with the city’s poor planning and enforcement of building and safety regulations often responsible for such deadly incidents.
Tearful relatives spoke of receiving desperate calls from factory workers begging to be freed from the inferno in the dark, poorly lit premises in the commercial hub of Sadar Bazar from around 5:00am (23:30 GMT).
One father who was trapped inside the four-storey structure made a desperate phone call to ask that his children be looked after.
“Monu, brother, I am going to die today,” the man, named Musharaff said in the recording of a call played by the ABP Hindi language news channel.
“Please take care of my kids. I can’t breathe. There are so many others here. Just can’t breathe,” he kept repeating in Hindi, eventually breaking down towards the end of the call.
Authorities do not yet know if Musharaff survived the blaze.
One survivor, Sabi Abbas, told AFP he had just finished work and was about to go to sleep when he heard screams from the third floor.
“I rushed to the floor and saw the wires were dangling and on fire as acrid smoke filled up the corridor,” he said, adding that he ran out of the building with his wife and daughters.
The building was home to a number of manufacturing units producing items including schoolbags and packing materials which only aided the spread of the blaze, officials said.
Prime Minister Narendra Modi tweeted that the fire was “extremely horrific”, as authorities said they would offer financial assistance to the victims’ families and to survivors.
Locals said the factory also made purses and jackets, and had just one entrance and 20 rooms on each floor that were connected by one internal stairway.
“Most of the casualties happened because of suffocation,” witness Mohammed Khalil told AFP.
“After the fire, people didn’t have any way to get out and I believe many were asleep and because of the smoke, they got suffocated.”
Others told AFP they believed the fire started on the first floor, sparked by exposed wires, before spreading to an area used to store foam and plastic chairs.
Outside a nearby hospital morgue, anxious relatives and friends gathered to identify the bodies.
Naushad Ahmad was looking desperately for his missing friend, who he was unable to reach on his mobile phone.
“I have been to the factory and this tragedy was waiting to happen,” he told AFP.
“There was only one exit and entrance to the building… People didn’t get a chance to escape.”
Sajjamuddin Ahmad spent two hours searching for his father-in-law and brother-in-law before discovering they were dead, he told AFP.
Families of the victims said they were mostly migrant workers from Bihar, one of India’s most impoverished states. Some of them were paid just 1,000 rupees ($14) a month, they said.
Police and fire officials said at least 58 others were rescued. The flames had been extinguished and they did not expect to find more bodies, they added.
The cause of the blaze is not yet known but Delhi’s fire services director told the Press Trust of India news agency that the site had been operating without the required fire safety clearances.
The building’s owner and manager were arrested later Sunday, police told PTI.
Factories and small manufacturing units in big Indian cities are often located in old, cramped areas, where the cost of land is cheaper.
Such units often also serve as sleeping quarters for poor, mostly migrant, workers, who save money by bedding down at their workplaces.
The blaze was the latest in a series of fire tragedies to hit India in recent years.
In 2016, more than 100 people were killed after a massive explosion during a banned fireworks display in the southern state of Kerala.
In 2011, at least 90 patients died after a fire in a Kolkata hospital. In 2004, 94 children burnt to death in a fire at a school in Kumbakonam in the southern state of Tamil Nadu.
In January 2018 17 workers were killed after a blaze in a plastic manufacturing facility in New Delhi.