Eighteen others, 14 of them firefighters, were also injured in the fire that broke out at a battery factory in Peeragarhi district just before dawn on Thursday, Delhi Police said in a statement.
More than 150 firefighters had been called to battle the blaze, which saw flames of more than 10 metres (33 feet) shoot up into the sky, according to reports.
An explosion later rocked the back of the building which collapsed into a heap of debris, giving off black toxic smoke and trapping many inside.
Two caretakers and a security guard were among those who were rescued.
Emergency services in New Delhi have been put on special alert following a series of high profile disasters in recent weeks.
A blaze that tore through a bag factory on December 9 killed 43 people, while nine others died in a later incident.
Delhi Police is investigating what triggered the blaze.
India is frequently rocked by fire disasters blamed on poor planning and lax enforcement of safety rules.
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