A crude bomb, kept inside a plastic packet, was recovered from near a wall of a public ground in Dudhnoi town, police said.
Unidentified persons also set ablaze three schools in Krishnai area of the town with two schools totally damaged and another partially.
A powerful bomb was recovered on National Highway 37 near New Dudhnoi area yesterday and four bombs were recovered from the railway tracks between Dudhnoi and Krishnai on November 8.
Unidentified persons also set ablaze three schools in Krishnai area.
Goalpara and parts of neighbouring Kamrup district have been witnessing violence since last month with non- tribals demanding exclusion of non-Rabha areas from the RHAC and protesting against the forthcoming Rabha Hasong Autonomous Council elections scheduled to be held between November 13 and 25 next.