A 15-member CBI team, including forensic experts, visited Rampurhat on Saturday to investigate the deaths of eighth people during suspected political violence in West Bengal's Birbhum earlier in the week.
The CBI team is being led by a Deputy Inspector General-ranked officer and the probe will be monitored by a Joint Director-level officer.
The central agency took over the probe on Friday and registered an FIR after Supreme Court orders. The team has to submit a report to the top court on April 7.
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Unknown assailants had thrown petrol bombs and set ablaze some 10 houses on fire in Bogtui village in the early hours of Tuesday, killing eight people including women and children, in a suspected fallout of the murder of a ruling Trinamool Congress deputy chief of the local panchayat. A total of 21 people have been arrested so far in connection with violence.