The Egra blast has prompted the Mamata Banerjee government to ask police and the Special Task Force to crack down on illegal firework factories across the state and scan those functional with “permission” to ensure whether the units are sources of crude bombs and explosives.

“The police in the districts and the Bengal STF have been preparing a database of such illegal fireworks units and will crack down on those very soon. The police will also visit those legal units to check for violations, if any,” said a senior state government official.

The development comes in the backdrop of the explosion at an illegal firework unit in East Mindpore’s Egra on Tuesday, in which 12 people have died so far. The owner of the illegal unit, Krishnapada Bag, aka Bhanu, died of his burn injuries at a hospital in Odisha on Friday.

Within hours of the Egra blast on Tuesday, chief minister Mamata Banerjee had asked the police to crack down on illegal firework units across Bengal.

“The police have to find out such illegal units in other places of the state. They (those units) should not function at all,” Mamata said at a news conference at the state secretariat Nabanna on Tuesday.

After the Egra tragedy, Opposition parties such as the BJP, the CPM and the Congress accused the local police and ruling party Trinamul of being hand-in-glove with the owner of the Egra firework unit that allegedly produced crude bombs.

Senior officers in both the state police and the STF said primary investigations revealed that illegal firework units were the prime source for the manufacture of crude bombs. They have also received intelligence inputs from workers of firework factories who said criminals and leaders of political parties often hired them to make bombs.

A senior police officer said in the past four days they had shortlisted at least a dozen areas where clusters of firework units were functional and discovered most of the incidents relating to crude bombs were taking place within a radius of 6km to 12km of these clusters.

The unit mapped a pocket near Naihati in North 24-Parganas having a cluster of fireworks units.

“Areas like Jagaddal or Bhatpara in North 24-Parganas are in the news for rampant use of crude bombs in political clashes or conflict between local rowdies. Interestingly, the fireworks clusters in Naihati are only 6km away from these pockets. We also have inputs that bombs are supplied by a few persons who usually prepare the fireworks,” said the police officer, adding that specific names of the pocket was being kept under wraps for the sake of the ongoing investigations.

Another source in the STF confirmed links between crude bomb hotspots and firework factories.

Keshpur is another pocket in West Midnapore known for violent clashes using crude bombs. There are a firework units on the way to Keshpur from Midnapore town.

There are several units at Champahati and Maheshtala in South 24-Parganas.

Surprisingly, the use of crude bombs is maximum on the southern fringes of Calcutta. On March 21 this year, three persons were killed in a fire at a firework factory in Maheshtala.

“The list is long,” said a police source. “Illegal firework units function fromdistricts such as Birbhumto Burdwan, East Midnapore to West Midnapore andeven in pockets of north Bengal districts like Cooch Behar.”