The CBI conducted searches on Saturday at multiple locations here in connection with the murder of West Bengal Chief Minister Suvendu Adhikari's aide Chandrakant Rath, officials said.
The search operation was conducted late Friday night which continued till the early hours of Saturday, they said.
The CBI has taken over the probe into Rath's murder from the West Bengal Police following a request from the state government.
The agency has formed a seven-member special investigation team under a DIG of Special Crime from Delhi, comprising some of the best investigators drawn from various units of the agency, officials said.
The team will report to the Joint Director, Kolkata.
Rath, the executive assistant to Adhikari, was shot dead in Madhyamgram on May 6, two days after the declaration of results of the fiercely fought West Bengal Assembly polls. The incident took place on a public road at Doharia in the Madhyamgram area.
The state police had arrested three persons in the case. Two accused - Mayank Raj Mishra and Vicky Maurya - were detained from Buxar in Bihar, while the third, Raj Singh, was detained from Ballia, Uttar Pradesh on Sunday.
Police said at least eight people were allegedly involved in the conspiracy and execution of the murder. They believe the attackers carried out a detailed reconnaissance before targeting Rath.