The body of a slain rhino with its horn missing was discovered by forest officials in Kaziranga National Park's Agratoli range on Friday, reported Press Trust of India.
Forest guards found the decomposed body of the pachyderm near Pohumara and Rangamati camps of the park.
A total of 21 rhinos have been killed so far this year.
According to the latest survey conducted in March, the population of rhinos presently stands at 2329 in the reserve.
The CBI has taken over three rhino poaching cases under the request of Assam state government.
The investigation agency has already taken over the cases where the animal's body parts were taken away. The poaching incidents took place in the park areas falling under Nagaon district, Golaghat and Karbi Anglong and date from July to September last year.
Only days ago, Unmanned Aerial Vehicles (UAV) were tested in the park for better surveillance. The drones are fitted with cameras to ensure better monitoring of the 480 square kilometre sanctuary especially during the monsoons when the reserve gets flooded.
The continual brutal rhino poaching has been troubling the Tarun Gogoi-led government. Despite citizen's protest and government's efforts, no bankable solution has come up yet.
Rhino horns, believed to have great medicinal qualities, are smuggled into Chinese and Southeast Asian markets where they have great demand.