The can bomb, which was planted by Maoists below a culvert, exploded while the bomb squad defusing it. One of the died was identified as Anil Singh, a Bihar military police constable in Bomb Disposal Squad.
The explosion also injured nine others, including three journalists of local TV channel covering the incident.
Earlier on the day, Maoists triggered a mine blast in Gaya district causing injury to a Jawan.
The sixth and final phase of Bihar Assembly poll ended without other major accidents.