Bablu Adhikary, Sonu Prasad, Amar Rajok and Nasim Qurashi were arrested last night from Lake Town by a special team of New Town Police, deputy commissioner of detective department of Bidhannagar Police Kankar Prasad Barui said.
On Monday, a gang of robbers barged into the firm's office, shot one round, held one at gunpoint and fled with Rs one crore before firing another round.
No one was injured in the heist as one of the bullets hit a wall and another misfired.
"We are interrogating them and have started a search for a few more persons involved in the crime and are currently hiding," he said.