The first ten-wheeler truck was searched at Rampur village on National Highway 60 and 350 bags of ammonium nitrate was seized from the vehicle on Tuesday.

The second ten-wheeler truck was tracked down in the Panchami area of Birbhum and another 305 bags of ammonium nitrate was seized as they were being unloaded in a warehouse in Talbandh village.

The warehouse belongs to one Bipul Mondal, who supplies explosives to stone quarries. However, Mondal is absconding after the seizure on Tuesday.

A labourer has been detained due to their involvement with the loading and unloading of the explosives, which were brought from the south Indian city of Hyderabad and from Maharashtra State. But the drivers and their helpers have given police the slip.

"The owners of the trucks have been identified and teams have been deployed to arrest them. We hope to arrest all those involved with the smuggling of explosives," said Birbhum's police chief N Sudheer Kumar.

He said they suspect the explosives were meant for the neighbouring state of Jharkhand, which has an active Indian Maoist presence.

But Indian Intelligence Bureau (IB) officials say these explosives could also have found their way to JMB militants from Bangladesh, who have set up a string of hideouts, training centres and bomb-making facilities across West Bengal.

Members of the group had been busted in 2014 after accidental explosions in Khagragarh in the Burdwan. But many others are believed to be at large and active.

"We have information that the JMB has set up hideouts in West Bengal after developing connections with local Islamist fundamentalists who are close to political parties. They could surely be one of the customers for explosives such as ammonium nitrate," said a senior IB official, on condition of anonymity.

Some top JMB activists recruited in India hail from Birbhum, a Trinamul Congress stronghold where the party's district secretary Anubarata Mondal controls dissent with a heavy hand.

JMB's India cell chief Mohammed Musa, now in jail, hails from Birbhum's Labhpur.

National Investigation Agency (NIA) officials have alleged in the chargesheet against him that Musa was planning to blow up the Mother House in Kolkata where the Missionaries of Charity are based.

They say the JMB was running a huge bomb making operation in West Bengal to supply its operatives in Bangladesh for attacking targets.

"We have received input from Bangladesh agencies and are determined to crush this racket," said an NIA official, who also wished to remain anonymous. "A small percentage of these seized chemical can bring down a high-rise building."