CBI sources said Shahabuddin has been brought to the agency headquarter for questioning in this case. The former Lok Sabha lawmaker from Bihar's Siwan constituency was lodged in Tihar prison.
The agency has told a Muzaffarpur court that his name has surfaced as an accused in the case and it needs his custodial interrogation.
The agency was granted the permission by the court to question him.
Shahabuddin is facing trial in more than 45 criminal cases and was moved to Tihar Jail in February this year on a Supreme Court order on a plea by Siwan native Chandrakeshwar Prasad, whose three sons were killed in two separate incidents.
Ranjan was shot dead on May 13 last year and his wife has accused Shahabuddin of having a role in the killing.
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