West Bengal police has arrested People's Committee against Police Atrocities leader Manoj Mahato, a key accused in the May 28 Gyaneshwari Express derailment.
Mahato was nabbed from a hideout at Madhupurkhal village early on Saturday morning, according to police sources.
However, his family has claimed that their son was picked up from their home in Birkar village.
A dozen-odd cases have been filed against Mahato.
Earlier, PCPA leader Umakanto Mahato, a key accused in the train derailment, was killed in an encounter with security forces at Mohanpur forest near Lothasuli in Jhargram district.
The CBI took over the Gyaneshwari Express investigation from the state police in June, and announced a reward of Rs 3 lakh for information leading to the arrest of three prime accused -- Bapi Mahato, Umakanto Mahato and Asit Mahato.
Bapi is in custody while Asit is still absconding.
The derailment of the Howrah-Kurla Gyaneshwari Express on May 28 by Maoists had claimed over 100 lives.