Three persons, from whom the horn was recovered, were arrested, they said.
They were identified as Babul Ali, Rafikul Islam and Mahesh Mehta.
Last year, poachers had killed 42 rhinos in the state.
Rhino horn is highly valued across the world for its so-called aphrodisiac qualities and is used in traditional medicine in Asia.
Demand for rhino horns has skyrocketed in recent years leading to drastic decline in the population of the shy animal.