Mahato was gunned down allegedly by Maoists at Baguria village under Ghatsila sub-division of East Singhbhum district on March 4, 2007. The incident is being probed by the CBI.
Following the incident, police had registered FIR against several Maoists cadres including prime accused Ranjit Pal alias Rahul, who was Bengal-Odisa-Jharkhand Area commander.
The MP's widow, Suman Mahato, an ex-JMM MP, had sought an NIA probe into the killing.
She also demanded adequate security for her.
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