Kolkata, April 3 -- The National Investigation Agency (NIA) has started probe by registering a "preliminary enquiry" into Malda violence case in which thousands of people on Wednesday blocked the two gates of the Kaliachowk-2 Block Development Office (BDO), holding staff including seven judicial officers "hostage" for hours before they were rescued after midnight.

The anti-terror agency initiated the preliminary enquiry late on Thursday after the Election Commission of India (ECI) formally referred the matter, sending a letter to its Director General.

The ECI's direction to the NIA came following the Supreme Court's order issued on Thursday, asking the poll panel that "a central agency, either CBI or NIA" probe the incident, pointing ou...