The building, in the neighborhood of Anaj Mandi, had no fire safety certification or emergency escape route. Windows were blocked with metal grills, flammable objects covered staircases and one of the building’s two exits was locked when the fire broke out, according to Atul Garg, the chief fire officer in New Delhi.

Many workers slept 10 to 15 in tiny, dimly lit rooms, where they spent their days making paper products, backpacks, plastic toys and clothing. Most were young Muslim men, some of them teenagers, who had come from distant villages in search of jobs that paid just a few dollars a day.

“There were no safety features,” Mr. Garg said.

The building’s owner, whom officials identified simply as Rehan, had also built at least one additional floor that did not meet minimum safety standards. He has been arrested and charged with crimes of culpable homicide not amounting to murder and “negligent conduct.”

Varsha Joshi, a commissioner for the local municipal corporation, told reporters that officials tried to inspect the building last week, as part of a bigger project closing illegal manufacturing units, but that some of the floors had been locked.

According to city data, at least 2,800 businesses have been found to work from residential buildings without proper paperwork in northern Delhi, though officials said the true figure could easily surpass 10,000.