The incident took place in Mohammadpur village as mound of earth caved in on five girls while they were digging soil for some function at their homes, Superintendent of Police Chandrika Prasad said.
While three girls, identified as Vibha Kumari (15), Shibu Kumari (13) and Manisha Kumari (10) were buried alive, two others sustained injuries, he said.
The bodies have been sent for post-mortem and the injured girls admitted to a hospital for treatment, Prasad said.
The district administration has provided an assistance of Rs. 1500 each to the family of all three victims for cremation under the state government's Kabir Atyesthi scheme, the SP said.