The case pertains to the siege of the Block Development Office (BDO) in Mothabari in April, where seven judges engaged in SIR-related duties were allegedly confined, and their vehicles attacked ahead of the Assembly elections.

According to NIA officials, Chowdhury, also known as Babu Chowdhury, is suspected to have played a key role in organising the siege. Investigators have reportedly obtained video footage in which he is seen making provocative remarks against the SIR process and judicial officers.

The agency also suspects his involvement in the attack on the judges’ vehicles while they were returning from the BDO office.

So far, 72 people have been arrested in the case, with charge sheets filed against 31 accused.

Earlier, the state police had arrested Indian Secular Front (ISF) candidate Shahjahan Ali Qadri, who was later taken into NIA custody and chargesheeted. Another ISF leader, Golam Rabbani, was also arrested in connection with the case.

Sources said Chowdhury was initially questioned by investigators soon after the NIA took over the probe in April, but he was not arrested at the time due to lack of sufficient evidence. Fresh evidence gathered subsequently led to his summons to Kolkata and eventual arrest.

The NIA stated that it is continuing with its probe to identify and track all accused involved in the various cases as part of the bigger conspiracy behind the large-scale pre-poll violence.

It said it is investigating over a dozen cases of mob protests and illegal detention of judicial officers during the Special Intensive Revision (SIR) exercise of electoral rolls in the Malda district ahead of the Assembly polls in the state.