At least 43 people, mostly migrant workers, were killed early on Sunday after a fire gutted a four-storey factory building in a congested area of India's capital, New Delhi. The victims were asleep when the fire broke out at 5am local time in 55-square-metre factory space on the third floor and soon engulfed the entire building. Thirty fire engines rushed to the factory, which is tucked inside congested lanes lined with many small manufacturing and storage units. Police said that most of the victims died due to asphyxiation and that the death toll was expected to rise. "Prima facie, it appears a short circuit caused the fire. Plastic material caused a lot of smoke. The case has now been transferred to the crime branch and a forensics team will arrive soon," M S Randhawa, Delhi Police spokesman, said. At Lok Nayak Jai Prakash Hospital, families waited to hear from doctors. "I have lost my brother. My brother is no more. My beloved brother. I looked for him everywhere, in all the hospitals, but he was in the mortuary," Zakir Hussain, 32, told <em>The National.</em> He rushed to search for his brother, Shakir, after receiving a call from Shakir's wife, who is pregnant with the couple's fourth child, and was waiting all morning for news. "Shakir called his wife after the fire broke out. He told her he might not survive, that the factory was filled with smoke and he was choking. His wife has been crying all morning," he said. "We came from Bihar [an eastern state] three years ago in search of work here." The blaze broke out in the city's old quarter, near Sadar Bazaar, New Delhi's largest wholesale market for household goods. Firefighters fought the blaze from 100 metres away because the alleyway was tangled in electrical wires and too narrow for vehicles to pass through, authorities at the scene said. Sabi Abbas, who was holding his young daughter Ayat, survived the fire after he and his family were alerted by the noise. "I was working on the first floor of the factory loading mirrors until 4.30am. I went to my room and had just lain down when I heard noise and screams from the third floor," he said. "I rushed there and saw wires dangling, and knocked on doors but no one answered. Then I ran out with my daughters and my wife." Mr Abbas lost all his belongings and savings of 5,000 rupees in the blaze, but said he was just "glad his wife and daughters were OK". Mehboob Alam was looking for news of his nephews, Mohammed Imran and Mohammed Ikramuddin. <br/> "My brother called me early in the morning asking me if his sons – my nephews – were OK. They called him after the fire broke out at the factory where they work. I went there to look for them but they were not there," he said. "I went to all the hospitals – I was hopeful they were alive but then I got a call from a relative who said Imran's body had been found. We are all losing hope [for Ikramuddin] now." Mohammed Mukhtra, who was also looking for his nephews, confirmed that one of the three was dead. "I don't know what to tell their parents in the village," he said. Adil Ahmed, a rickshaw driver who lives metres from the factory building, said the authorities should look into how the factories were allowed to operate in an overcrowded area, which is a fire hazard. "We want an investigation into this matter against the current administration. Why do they allow these factories to operate in these congested lanes?" he said. Sunil Choudhary, New Delhi's deputy chief fire officer, told AFP that they had rescued 50 people. They were "labourers and factory workers sleeping inside this four- or five-storey building", he said. Mr Choudhary said<span style="background-color:rgba(255, 255, 0, 0.3)"> </span>the fire had been extinguished but rescue operations were ongoing. Fire Services chief Atul Garg said the blaze was put out by 25 fire trucks and that the rescue operation was completed. Distraught people appeared at the site of the blaze and at the three hospitals. The Press Trust of India news agency quoted Manoj, who uses one name, as saying that his brother Naveen, 18, was working in a handbag manufacturing unit in the building. “I got a call from his friend informing that he has been injured in the incident. I have no clue which hospital he has been taken to,” he said. New Delhi’s chief minister, Arvind Kejriwal, visited the scene of the fire and promised victims’ families compensation. Manoj Tiwari, a Bharatiya Janata Party lawmaker from New Delhi, said most of the casualties occurred on the third floor of the building. Prime Minister Narendra Modi described the fire as “extremely horrific". “My thoughts are with those who lost their loved ones. Wishing the injured a quick recovery,” Mr Modi tweeted. Authorities are providing all possible assistance at the site of the tragedy, he said. Many factories and small manufacturing units in big Indian cities are often located in old, congested areas where the cost of land is relatively cheaper. Such units often also serve as sleeping quarters for poor, mostly migrant workers who try to save money by sleeping at their workplaces. Building fires are common in India, where construction and safety regulations are often flouted by builders, owners and occupants. In 1997, a fire in a movie theatre in New Delhi killed 59 people. In February this year, 17 people were died in a fire at a six-storey hotel in the Indian capital that started in an illegal rooftop kitchen.