The National Investigation Agency on Saturday arrested two key conspirators in a 2022 blast case amid an attack on the probe agency's team by a crowd in West Bengal's East Medinipore district, an official said here.

An NIA officer was injured and a vehicle belonging to the probe agency was damaged in the attack, a spokesperson of the federal investigating agency said.

Saturday's incident brought back memories of January 5 when three officials of the Enforcement Directorate were attacked by a mob in North 24 Parganas district's Sandeshkhali during a search on the premises of then Trinamul Congress leader Shajahan Sheikh in connection with alleged irregularities in the public distribution system.

A spokesperson of the NIA on Saturday said, "In a major breakthrough in West Bengal's Bhupatinagar blast case, in which three persons were killed in December 2022, the NIA arrested two key conspirators amid stiff resistance from an unruly crowd in the state's East Medinipore district." The duo -- Balai Charan Maity and Manobrata Jana -- were arrested after extensive searches at five locations, including the house of Jana, where locals tried to obstruct the NIA team.

The crowd tried to stop the NIA team and its security component from moving towards the Bhupatinagar police station to complete the arrest formalities. The NIA has lodged a complaint at the local police station in this regard.

The NIA spokesperson said Jana and Maity were found to have conspired to manufacture and explode crude bombs to spread terror.

Three persons were killed when an explosion ripped apart the kutcha house of Rajkumar Manna in Bhupatinagar on December 3, 2022. Rajkumar Manna, Biswajit Gayen and Buddhadeb Manna were grievously injured in the blast and later died.

The state police initially registered an FIR on December 3, 2022, against the three men killed in the explosion but the provisions of the Explosive Substances Act were not applied. Subsequently, a writ petition was filed before the Calcutta High Court with a prayer for transferring the case to the NIA.

The NIA took over the case on June 4, 2023, on the high court's order dated March 21, 2023, and re-registered a case under various sections of law, including the Explosive Substances Act.

During the investigation, the NIA uncovered the role of several other accused in the case, including Manobrata Jana of Naruabila village and Balai Charan Maity of Ninaruya Analberia.

The two men had actively participated in the conspiracy to make crude bombs and extended support for the same, the NIA found in its probe, which led to searches and arrests on Saturday.

The two arrested will be produced before the Special NIA Court in Calcutta. A probe into the case was underway, the spokesperson said.