The CBI apprehended the driver of an e-rickshaw on Thursday who allegedly transported petrol that was used to set ablaze houses in Birbhum's Bogtui village, resulting in nine people's deaths, an official said.
Ritan Shiekh was arrested from his house in Bogtui in the early hours, he said.
"He was identified from the CCTV footage. Also, his name cropped up in statements given by other suspects arrested and witnesses," the CBI official told PTI.
Ritan went missing after the massacre, he said.
"He used to go into hiding during the day, and return home in the dead of the night," the official said.
The CBI was on the hunt for him, he said.
With this, the CBI has made six arrests in the case after taking over the probe from the West Bengal police on the direction of the Calcutta High Court. The agency has also taken custody of 22 persons earlier arrested by the police.
The CBI searched Ritan's house after his arrest, the official said.
indNine people died of burn injuries as their houses in Bogtui were allegedly firebombed after the murder of local TMC leader Bhadu Sheikh.