A tigress and her two cubs were found dead on Friday evening in Umred Paoni Karhandala Sanctuary in Maharashtra's Nagpur district, an official said.
It was suspected that poisoning was the cause of death but it was yet to be confirmed, he said.
Pench Tiger Reserve field director Ravikiran Govekar, in a statement, said the carcasses were found near an agricultural field, and the half-eaten body of a cow was lying nearby.
It is suspected that they died due to poisoning, but nothing can be confirmed unless medical reports are available, he said.
"A probe has begun. Autopsy of the carcasses will be carried out on Saturday," the statement added.