Authorities said an electrical short circuit appeared to cause a fire that killed at least 43 people in a factory in central New Delhi early Sunday. Relatives of the workers who were trapped inside identified the dead from photos on police officers' phones.

The fire broke out minutes past 5 am local time when about a 100 people, mostly workers of a bag-making factory operating in the building, were sleeping inside, CBS News' Arshad Zargar reports.

Assistant New Delhi police commissioner Anil Kumar Mittal said that "the fire appears to have been caused by electric short circuit," adding that authorities were investigating whether the factory was operating legally.

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The building's owner, Rihan, who goes by one name, was detained on suspicion of culpable homicide not amounting to murder, Mittal said.

A woman weeps as she waits outside a mortuary to receive the body of her relative who died in a fire that swept through a factory where laborers were sleeping, in New Delhi, India, on Sunday, December 8, 2019. Reuters

Firefighters had to fight the blaze from 100 yards away because it broke out in one of the area's many alleyways, tangled in electrical wire and too narrow for vehicles to access, authorities said.

"Most who've died were sleeping when the fire broke out and died due to asphyxiation," Sadar Bazar's assistant commissioner of police told AFP.

A resident of the area, Mohammed Naushad, said he was woken by people wailing at around 4:30 a.m. He went outside to find smoke and flames shooting out of a building near Sadar Bazaar, New Delhi's largest wholesale market for household goods. Inside, he found the fourth floor engulfed in flames. One floor below, he saw "20 to 25 people lying on the floor."

"I don't know if they were dead or unconscious, but they were not moving," Naushad said.

He said he carried at least 10 people out of the flames on his shoulders and into the arms of emergency responders.

Maisuma Bibi, a day laborer making plastic handbags, survived the blaze. She said she was sleeping in a room with about 18 other women and children on the building's first floor when she woke to find a bag full of plastic parts on fire. Her brother-in-law carried her to safety, she said.

Outside a mortuary that was guarded by dozens of police officers, some of the workers' relatives said they had received phone calls from the men trapped inside, who begged them to call the fire brigade.

Many of the men were migrant workers from the impoverished border state of Bihar in eastern India, relatives said. They earned as little as 150 rupees ($2.10) per day making handbags, caps and other garments, sleeping at the factory between long shifts.

Many of the victims were asleep when the blaze began, according to Yogesh, a police spokesman who uses one name.

Dr. Kishore Singh said rescuers brought victims to his government-run hospital and two others in the city. Another 16 people were being treated for burns or smoke inhalation and were in stable condition, Singh said.

Police barred relatives from entering Lok Nayak hospital, where some of the victims were taken. Relatives of the workers cried, consoled one another and jostled for information.

"I was told by someone my nephew is inside, but I haven't seen him," said Mohammad Moti, who was searching for his 22-year-old nephew, Mohammad Chedi.

Fire Services chief Atul Garg said it took 25 fire trucks to put out the blaze. About 60 people, including some of the dead, were taken out of the building, Mittal said.

New Delhi's chief minister, Arvind Kejriwal, appeared at the scene of the fire, promising victims' families compensation.

Prime Minister Narendra Modi described the fire as "extremely horrific" in a Twitter post.

The fire in Delhi’s Anaj Mandi on Rani Jhansi Road is extremely horrific. My thoughts are with those who lost their loved ones. Wishing the injured a quick recovery. Authorities are providing all possible assistance at the site of the tragedy. — Narendra Modi (@narendramodi) December 8, 2019

Fires are common in India, where building laws and safety norms are often flouted by builders and residents. In 1997, a fire in a movie theater in New Delhi killed 59 people. In February this year, 17 people were killed by a fire in a six-story hotel in the capital not far from Sunday's blaze that started in an illegal rooftop kitchen.