"The chargesheet was filed at a special NIA court in Patna Thursday," a district police official said.
The chargesheet was filed against Ansari after a thorough probe by an NIA team.
Ansari, a resident of Jharkhand's capital Ranchi, is in custody. He was arrested at the Patna railway station after a bomb exploded on the platform few hours before Modi's rally at Gandhi Maidan here. At least six people were killed and nearly 100 injured in a series of blasts during the rally.