Patna: Thursday's explosion at the illegal firecracker factory in Nalanda's Sohsarai, which claimed six lives and left 18 injured, has left many questions unanswered.

A similar explosion had occurred in the same building on April 9, 2012, though the intensity of the blast was lesser compared to the latest one.

The owner of the factory, Mohammad Sarfaraz, was arrested and jailed for putting residents at risk as the factory was located in a crowded locality and was also found to be running without licence.

Local residents believe Sarfaraz, who died with four of his family members in Thursday's blast, had secured bail in the earlier case lodged with the Sohsarai police station (case number 39/12) soon after his arrest and started manufacturing crackers under the brand name Sayeed Fire Works.

Local residents said they had complained against the factory to the police and the district officials.

"At times policemen used to visit the factory secretly after residents complained but the factory never stopped functioning except during the brief period when Sarfaraz was in jail," said a resident of Khashganj where the factory was located.

The police recovered a large number of wrappers of the firecracker company and also its registration from the debris. A container of aluminium weighing over 40kg besides a huge consignment of manufactured firecrackers and raw material were also found in the debris.

The question arises why the police and the district officials didn't take notice of the illegal activities. The locals alleged it was because of a nexus between the factory owner, the police and administrative officials.

Sources said the firecrackers manufactured at Sarfaraz's unit were supplied to the local market as well as other parts of the state.

Sarfaraz's neighbour, who was injured in the blast, claimed the family had been in the business for over two decades. Sarfaraz, a native of Bakra Chorasan village under the jurisdiction of Giriyak police station in Nalanda, took the house of a certain Jameela Khatoon on rent.

Jameela shifted to Kamruddinganj under the jurisdiction of Laheri police station, after renting out her house to Sarfaraz.

"The tremor of the explosion was felt in a radius of 2km, which gave credence to locals' perception that powerful bombs were being manufactured at the unit," a resident said.

Nalanda superintendent of police Sudhir Kumar Porika said an eight-member team from the state anti-terrorism squad visited the site and collected samples of the material used for making firecrackers. A team of the forensic experts were assigned to assist the district police in the probe.

Sarfaraz had told the police that the fire broke out in the house-cum-factory around 10.30pm on Thursday when he was trying to light an incense stick.

At least seven houses were demolished and 30 other buildings partially damaged in the incident, an investigating officer said.

Nalanda district magistrate Thiyagrajan S.M. said a three-member probe committee would submit its report within three days.

The district administration, he said, would launch a crackdown against illegal firecracker units.