Thirteen workers have died in a fire at a suspected illegal garment factory on the outskirts of Delhi in India.

The workers were sleeping when the blaze started in the early hours of Friday on the ground floor of a narrow building, which was being used to make leather jackets in Sahibabad, a suburb of Delhi.

"The fire broke out at a factory in a residential area of Sahibabad around 4:30am. Thirteen people, who were sleeping there have died and another two or three people are getting treated at the hospital," Bhagwat Singh, local police spokesman, told AFP news agency.

Abbas Hussain, a local fire officer, said two workers were rescued after they woke up when the fire started.

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"The two of them woke up by chance and say they screamed for others to wake up while running towards the terrace but others didn't wake up, perhaps it was already late," he said.

Hussain said workers died of smoke inhalation and described piles of leather stacked in the building's narrow staircase and cramped workshop, adding that the factory was most likely illegal.

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"From what we see, there was nothing proper and the factory must surely not have been a legal one but we can say for sure only after a proper investigation," he said.

A dozen fire engines doused the flames after battling them for several hours. The cause of the fire is being investigated.

The fire is yet another blight on India's poor record for workplace safety where deadly accidents are commonplace.

Eight workers were killed last month in a huge explosion at a firework factory in the southern state of Tamil Nadu while a blaze in a firecracker workshop killed 15 people in May 2014 in central Madhya Pradesh.

A fire at a factory where leather bags were being stitched killed six workers in November 2013 in New Delhi.

Some of the victims were trapped inside the building and burned beyond recognition.

South Asia's lucrative garment industry has a particularly alarming safety record, with watchdogs saying safety rules are routinely flouted.

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A huge fire triggered by a boiler explosion at a packaging factory just north of Dhaka, Bangladesh, left 25 people dead in September.

In November 2012, at least 111 workers were killed when a devastating fire engulfed a nine-storey garment factory outside Dhaka.

The accident was followed by an even bigger disaster six months later when 1,138 people died after a clothing factory complex collapsed, trapping more than 3,000 workers.

The Rana Plaza tragedy triggered international outrage and put pressure on European and US clothing brands to improve pay and conditions at the factories that supply them.

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Source: Agencies