Delhi Fire Service Director Atul Garg, who was present at the site, said: "Five firemen, who went into the building to douse the fire and were trapped, have been rescued. They were injured and have been sent to the hospital for medical aid."

The firemen were trapped inside the building after a sudden blast.

An eyewitness present on the spot told IANS: "There is a citizen among the 6 injured, who have been evacuated by fire service personnel. The remaining five are fire fighters. The person may have been a factory worker. However, it has not been confirmed yet."

The factory is being run by the Okaya company, which manufactures batteries.

Hospitals around the are have been alerted.

Earlier, several people including few fire fighters were reported to be trapped inside the factory in Peeragarhi, the Delhi Fire Services (DFS) said here on Thursday.

According to the DFS chief Atul Garg, "A call for fire in a factory was received at 4.23 a.m. on Thursday, accordingly, 7 fire tenders were sent to the spot. However, the fire was followed by a sudden blast, due to which the building collapsed."

However, the number of people trapped inside the structure is not known yet. In total 35 fire tenders are on the spot as the rescue operation continues.