The carcass was spotted on Saturday.
On Friday, a cub and a cow were found dead in the sanctuary.
The carcass of the second cub was spotted almost 50 metres away from the place where the cow's body was found, Field Director of Dudhwa Katarniya Reserve Forest Ramesh Pandey said.
The cubs were 12 months to 15 months old, he added.
Pandey said according to post-mortem examination conducted by experts from Indian Veterinary Research Institute (IVRI), Bareilly, there is a possibility that the cubs were attacked by a bigger carnivorous animal.
He said presence of a bigger leopard as shown by the camera trap, pugmarks and a partially-eaten carcass of the cow corroborate the theory.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)