A woman who had suffered burns in the violence at Bogtui village in Birbhum district last week died in a hospital on Monday, raising the toll to nine, a police officer said.
Out of the nine deceased, seven are women and two are children.
"The woman, Najema Bibi, had nearly 65 per cent burn injuries. Her condition deteriorated last night following which she was put on ventilation in the Rampurhat Government Medical College and Hospital. She died this morning," the police officer said.
Three persons, including a boy, are still undergoing treatment at the same hospital.
The CBI probing the case could not record the statement of Najema on Sunday, when its sleuths visited the hospital, as her condition was critical.
"We could not talk to her as her condition was not suitable for that. She could have been a good source of information regarding that night's attack and the killing," a CBI officer told PTI when contacted.
Chief Minister Mamata Banerjee had visited the injured persons in the hospital on March 24 during her visit to Bogtui.
On the night of March 21, eight people were burnt to death after a number of houses in the village were set on fire by unknown miscreants, in a suspected fallout of the murder of a local Trinamool Congress leader.
The CBI is now investigating the case on the order of the Calcutta High Court. Earlier, the matter was probed by an SIT formed by the West Bengal government.
