Sources told rediff.com that the bomb, which was attached to a battery, was low in intensity.
The explosion takes place a day ahead of the elections.
Sources say it is too early to say whether it was the handiwork of a terror outfit.
It could be a blast with a political angle to it, sources point out.
Madhubani has had a tryst with terror only when it was found that there were recruitment camps here.
As per an intelligence dossier, Madhubani along with Araria and Sithamarhi were used as recruiting grounds.
Investigations are on to ascertain the nature of the blast, but at the moment the police are ruling out a terror strike.
Complete Coverage: Lok Sabha Election 2014
TDSAT upholds telcos' 3G roaming agreement, quashes fines
Why the Boogie Woogie star is fighting an election
'There is no Narendra Modi factor in the rural areas'
Sixth phase: Puducherry records 83 pc polling, Mumbai lags at 53 pc
'Even a butcher is shy' of Modi: Lalu