The by-poll is scheduled for June 2.
Siwan district judge in-charge, S K Pandey hearing his anticipatory bail application ordered not to arrest him till June 6.
An FIR was registered against the RJD candidate on Monday night at Bhagwanpur police station here on the basis of a complaint by district agriculture officer Bharat Pratap Singh.
The district agriculture officer in his complaint said he along with trainee IAS officer Amit Ranjan Ghosh were checking vehicles at Bhagwanpur market area when they stopped a vehicle of the RJD leader's carcade which did not have the Election Commission's approval.
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He had also alleged that NDA leaders were moving around in Maharajganj parliamentary constituency area in cars fitted with red beacon lights in utter violation of the poll code.
His supporters also allegedly snatched away the video camera of the trainee IAS officer.
Prabhunath Singh is pitted against JD(U)'s P K Shahi and Congress' Jitendra Swami in the by-election.