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The blast took place on Friday at Bahadurgarh industrial town in Jhajjar district.
"Four laborers were killed and 30 others, including women and children, were injured," an official at deputy commissioner's office in Jhajjar said. "Preliminary investigations reveal bursting of boiler in the factory caused blast."
Following the blast, authorities rushed fire tenders and police to the spot to carry out rescue work.
"We have also called in a team of the National Disaster Response Force (NDRF) from Delhi," the official said. "The rescue work is underway at the spot to find out if anyone is trapped in the debris of the factory."
Officials said the injured were being treated at two local hospitals.
Locals said the blast also damaged several buildings and smashed windshields of several vehicles parked in the vicinity.
Police have registered a case and ordered investigations into the blast.