The Bengal Special Task Force (STF) arrested Md Nazrul Islam, the alleged kingpin of the chain that supplies fireworks produced at illegal factories to buyers across the state, from Calcutta airport late on Thursday night.

Nazrul's supply chain included sourcing fireworks from the illegal factory at Duttapukur in North 24-Parganas, where nine persons were killed in an explosion on August 27.

A source said STF nabbed Nazrul, who had fled to Chennai within hours of the explosion, after he arrived in Calcutta on Thursday night. He was produced before a court in Barasat on Friday and sent in eight days' police remand.

"We came to know about Nazrul after the seizure of five trucks loaded with tons of illegal firecrackers. He used to operate the racket by involving at least a dozen illegal fireworks factories, including the Duttapukur unit where nine people died in an explosion last week. He also used to fund the supply of raw material to these units," said a senior officer in Bengal STF.

Cops of the Bengal STF on August 29 evening seized five truck loads of illegal firecrackers from two different points in North 24-Parganas. Two of the trucks were seized from a parking lot in New Barrackpore and three were detained from the Amdanga police station area.

Following the seizure of the trucks, the STF arrested two persons for transporting illegal firecrackers to various pockets of the state. Following interrogation of the duo, the STF came to know about Nazrul and his modus operandi.

The Bengal STF had started a specific case under various sections of the Indian Penal Code, including the Indian Explosives Act, Explosive Substances Act, and Fire Services Act, against Nazrul and others involved in the illegal racket.

"We were on the hunt for Nazrul as soon as we came to know about his activities in the racket. We got information that he had fled to Chennai within a few hours of the August 27 explosion. We received a tip-off on Thursday evening about his return from the southern state to Calcutta. As soon as he landed in the city, we did not delay to arrest him," a source said.

A source said before STF arrested Nazrul, the Duttapukur had come to know about his involvement in the illegal unit. The police have learnt that Nazrul was involved in the production and marketing of illegal fireworks at Duttapukur, while he had his godown in Barasat from where tons of firecrackers were seized.

The police and STF have so far recovered around 100 tons of illegal firecrackers worth Rs 12 crore from various places and most of these were part of Nazrul's racket.

"You can easily imagine the volume of illegal business that Nazrul and his people have been running for years. We have information that the explosion at the illegal unit in East Midnapore's Egra did not have an impact on the Duttapukur factory. It functioned as if nothing had happened," a source in the STF said.

At least 12 persons were killed in an explosion at an illegal fireworks unit in Egra on May 16. After the explosion, the state government asked all the districts to crack down on such illegal units and stop the production of illegal firecrackers.

"It is beyond imagination that such a large-scale racket had been running and the police were in the dark. During the investigation, we will try to find out whether there were any big players involved in the racket," said a source in the STF.