The explosion brought down the entire two-storied building housing the factory besides three adjoining houses. It took more than an hour for the fire fighters to control the blaze.

Around 150 labourers were in the factory at the time of the blast. When reporters reached the scene, all that was left was a huge pile of smouldering debris and vessels, slippers, pieces of torn clothes and blood stained tyres strewn across the devastated areas.

The explosion at Khusrupur, about 50 km from the state capital, was heard more than three kilometres away. As a deafening blast rent the air at 12.30 pm, a huge cloud of dust and shards of the building filled the atmosphere.

The explosion brought down the entire two-storied building housing the factory besides three adjoining houses. It took more than an hour for the fire fighters to control the blaze.

Around 150 labourers were in the factory at the time of the blast. When reporters reached the scene, all that was left was a huge pile of smouldering debris and vessels, slippers, pieces of torn clothes and blood stained tyres strewn across the devastated areas.

He also did not rule out the possibility of an LPG cylinder causing the blast. "The explosion could have occurred due to some high grid explosives among the crackers in the factory," he said.

Patna SSP Kundan Krishnan, who visited the blast site, said police would investigate whether the factory was making firecrackers illegally.

Factory owner Mohammad Hakim has been detained. Residents were surprised that authorities had given a licence to such a dangerous industry to be set up in a crowded neighbourhood.

According to rural SP G P Sinha, when the permit for the setting up the factory was given, the area was not so thickly populated.

"To the public this was a match box and firecracker factory but I am sure illegal explosives were being made here," said Shaliesh, a resident of Khusrupur.

Vinita Devi, who lost her two sons and a daughter in the explosion, could not utter a word and kept crying though. People around her said her children were working in the factory for the last five years.

Many of the factory workers are believed to be young children and that was borne out when rescuers started bringing corpses out.