The grenade lobbed at the house at around 8 PM last night damaged some window panes and some walls, besides injuring Ram Kumar Rai, they said.
No individual or group has claimed responsibility for the crime, sources said adding that Rai, a worker at the house, was rushed to a nearby hospital.
Risom and his family members were not present at the house because they are staying at government quarters at the VIP area at Babupara.