The carcasses were spotted near the National Highway-11 and buried on Wednesday and a case was lodged on a complaint by the forest department on the same day, Station House Officer (SHO), Dudu, Hari Singh Dayal said today.
"It is suspected that the langurs were beaten and dumped there," the officer said.
The Humane Society International (HSI), an organisation working on animal protection issues, has offered a reward of Rs 1 lakh on information on people involved in incident.
The grey langur is a protected species under Schedule II of the Wildlife Protection Act, 1972. That means harming them is against the law and a punishable offence, it stated.
Animal activist Babu Lal Jaju claimed that the animals were beaten and a acid-like chemical was splashed on them.