"Prima facie it appears packaging of the fire crackers were going on, but no machines have been found", he said.
In November, a massive fire at a plastic factory in the northern city of Ludhiana left 13 people dead, including three firefighters who were killed when the building collapsed.
Union Minister Harsh Vardhan, Bharatiya Janata Party (BJP) leader Manoj Tiwari and Leader of Opposition in Delhi assembly Vijender Gupta and North Delhi Municipal Corporation Mayor Preety Agarwal also reached the spot. "The rescue operations are underway as more people are suspected to be trapped inside the factory", said officials. 15 fire tenders were rushed to the spot and soon contained the level 4 category fire. Earlier, the police had said that Jain was running the unit in partnership with one Lalit Goel.
However, Delhi Police put the number of casualties in the incident at 4.
The Delhi government has ordered an inquiry into the blaze.
Delhi Chief Minister Arvind Kejriwal said he was also keeping a close watch on rescue operations.
On December 28, at least 14 people, 11 of them young women in their twenties and thirties out, had lost their lives after a deadly fire ripped through two upscale restaurants in Mumbai. "May those who are injured recover quickly", Modi said in a tweet on Saturday.
Delhi Urban Development minister Satyendar Jain said an inquiry has been ordered into the incident. Several casualties reported. Monitoring the situation.