The Criminal Investigation Department on Thursday made a major breakthrough in the probe into the murder of BJP leader Manish Shukla as sleuths seized three motorcycles belonging to the alleged assailants and a carbine and three pistols used in the crime.

The former councillor of Titagarh municipality had been gunned down at Purani Bazar near Titagarh police station on the night of October 4.

The seizures were made hours after the CID arrested suspect Subodh Yadav alias Subodh Rai, a resident of the Khatal area of Barrackpore, on the basis of a lead provided by one of the three persons held earlier.

Subodh, a Trinamul activist and allegedly close to Barrackpore municipality’s former chairman Uttam Das, was picked up from his home on Wednesday night. His arrest was registered in the early hours of Thursday at the end of a marathon interrogation.

A police source said Subodh faced twin charges of being part of the conspiracy to kill Shukla and harbouring the assailants. He was produced in a Barrackpore court and remanded in police custody for 14 days.

CID sources said based on Subodh’s revelation, a raid was carried on a glass factory near the Sodepur railway bridge and it culminated in the recovery of the carbine, along with three pistols, on Thursday afternoon.

“All the weapons, including the carbine, are country-made,” said a CID official. “It is being examined who procured the weapons and from where,” he added.

Another CID sleuth said Subodh, the fourth person to be arrested in the murder, was one of the key persons involved in the conspiracy and had provided shelter to the contract killers.

“The entire plan to eliminate Manish Shukla was hatched at the residence of Subodh. He provided shelter to the contract sharpshooters who were at least four in number and came to Barrackpore from outside a few days before the murder,” he said.

Though the sleuths are yet to arrest the four suspected killers engaged by prime accused Khurram Khan, they have come to know that the sharpshooters were staying at a multi-storied building on Dakshin Panchanantala Road in ward 4 of Barrackpore town. The flat has since been sealed by the police.

“Subodh had arranged the flat to lodge the hired shooters. Names of a few more persons suspected to be involved in the murder have also surfaced. Their roles are being examined,” the sleuth said.

Priyanka Tibrewal, an advocate, filed a PIL in Calcutta High Court on Thursday seeking transfer of the probe into to the CBI.