Nine people were burnt to death in Bengal's Birbhum in an alleged reprisal for the politician's murder.
The murder of a Trinamool Congress leader, which had allegedly led to a revenge attack in which nine people were burnt to death in West Bengal's Birbhum district last month, should be probed by the Central Bureau of Investigation (CBI), the Calcutta High Court ruled on Friday.
The High Court had earlier ordered a CBI investigation into the gruesome Birbhum killings that took place in Bogtui village on March 21.
The court had been requested to order a CBI probe into the murder of Trinamool leader Bhadu Sheikh as well with a petition that said the two incidents were linked.
The judges ordered the transfer of the murder case of Sheikh from the state police to the CBI for a thorough investigation.
The state police chief had on March 22 said that the violence at Bogtui took place within an hour of the murder of Sheikh, the deputy chief of the local panchayat.
The place of the murder of Sheikh is about a kilometre away from Bogtui.
CBI investigators on Thursday arrested four West Bengal residents from Mumbai, suspected of being involved in the Birbhum killings, an officer of the agency said.
These were the first arrests made by the agency since it took over the probe into the killings.
"The four accused had direct involvement in the killings and had fled from Bogtui to Mumbai on March 22. They were apprehended from their hideout early on Thursday morning after their mobile tower location was tracked.
"Of the four arrested accused, two persons -- identified as Bappa and Shabu Sheikh -- were named in an FIR lodged in connection with the killings. The other two were identified as Taj Mohammad and Serajul," he said.
The killings of nine people, who were burnt alive, after assailants threw petrol bombs on several houses in the village was earlier being probed by a Special Investigation Team formed by the state government.
The CBI had registered a case against 22 people on March 25 in connection with the incident.