A massive fire swept through a New Delhi factory on Sunday, leaving 43 people dead and many others injured, said the Indian police.

Most of the fatalities were reported among the laborers sleeping inside the building, said the local news agency Asia News International, citing police sources.

According to police officials at the scene, dozens of workers were inside the factory when the fire broke out in Sadar Bazar area.

The factory was operating in a residential area. Firefighters rushed to the scene after the fire was reported early morning.

The fatalities are feared to rise as some sustained grave injuries.

Read more: Fire in Delhi factory: Blazes kill at least 43 in India