The accused --Rakesh Yadav and Gajendra Sharma-- were arrested yesterday, a press release issued today by the National Investigation Agency (NIA) said.
While Yadav was arrested from Motihari, Sharma surrendered in a court in Raxaul, it said.
The NIA was looking for the duo for their suspected links to three other persons --already arrested by the agency for their alleged involvement in the case.
The trio -- Moti Paswan, Uma Shankar and Mukesh Yadav -- were arrested last month by police from East Champaran district of Bihar.
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These three accused had claimed to have got Rs three lakh to plant improvised explosive devices (IEDs) at Ghorasahan railway station in Motihari on October 1, 2015.
Bihar Police has reportedly recovered the IEDs.
This case was first registered by Bihar Police and later taken up for investigation by the NIA.