Power distribution company BYPL claimed that the fire at a factory in Anaj Mandi here appeared to have started in some "internal system" of the building.
A massive fire swept through the building having manufacturing units, in north Delhi's Anaj Mandi area around 5.22 am, leaving at least 43 people, mostly labourers, dead, police said.
Thirty fire tenders rushed to the spot after the fire department received information about the incident.
A team of BSES Yamuna Power Limited (BRPL) rushed to the spot after getting information of fire and immediately discontinued the electricity supply, according to a discom spokesman.
"It appears that the fire started in the internal system of the building," he said.
The fire occurred on the second and third floors of the factory building operating from the residential area.
The electricity metres of the building were placed on the ground floor and were found to be intact, the spokesman added.