Superintendent of Police P Kannan said the bomb exploded at the door of Hasan's house.
Hasan, JD(U) MP from Begusarai Lok Sabha seat, was not present in the house at the time of the blast as he is New Delhi.
Kannan said an investigation was on in.
The MP's personal secretary Aftab Alam, who was in the house at the time of the blast, alleged it was the handiwork of Maoists.
Maoists, he said, had pasted posters on the house earlier calling for boycott of the assembly polls in 2005.
