All firecracker units at Kalyani in Nadia district, including the one where an explosion killed four women labourers on Friday, had been offered an alternative location to set up the factories, but none of them accepted the proposal, said a member of an association of firecracker makers.

The alternative location was offered at Char Kanchrapara in Nadia district as part of the state government's efforts to set up green cracker clusters across the state.

The reluctance of the units to relocate to the proposed cluster was confirmed by Babla Roy, a member of a state government-appointed committee and chairman of Sara Bangla Atasbaji Unnayan Samiti, a TMC-affiliated union.

The committee was constituted to oversee the establishment of green cracker clusters.

“I persuaded them to shift to Char Kanchrapara, where the government proposed to give land free of cost and extend assistance in obtaining required manufacturing licences for green firecrackers. But none agreed as they felt the new site was too far from their home-cum-factory,” said Roy, before criticising police for lack of surveillance that allowed the units to operate in areas with high population density.

Roy further alleged that Opposition parties played a role in misleading the units.

"They were offered land free of cost and the necessary assistance, yet they refused. It seems the Opposition parties discouraged them from relocating,” he added.

According to him, this resistance hindered the establishment of a regulated cluster in Kalyani despite the government’s best efforts.

Instead of relocating to the proposed cluster site, several unit owners in Kalyani have been putting pressure on the association to ensure necessary clearance to operate in areas where they have been located for years.

Sources in the Nadia administration have said only two of the firecracker units based in Kalyani have required licences, but major steps could not be taken because of the state's policy and political pressure.

“The state does not support forceful evacuation of people as their livelihood would be hurt and at the same time, the units have blessings of political leaders,” said a senior official.

A firecracker unit owner in Kalyani admitted that they had been offered land free of cost.

“But we could not relocate as we needed to invest a handsome amount to set up the factory infrastructure there. We don't have that much money,” said the unit owner.

On Saturday, a team from the Forensic Science Laboratory examined the blast site and collected samples for investigation. “We would send our report to the police for further action,” forensic expert Debasish Saha said.

Earlier in the day, the police conducted raids on multiple firecracker units and seized large quantities of explosive materials and unfinished firecrackers.

Khokon Biswas, the owner of the unit where the explosion took place, was remanded in police custody for 10 days by the additional chief judicial magistrate's court in Kalyani.