Two tigers and an elephant were found dead on Thursday in Hirikere forest area under the Bandipur National Park limits.
The decomposed carcass of a three-year-old male tiger and a two-year-old female tiger were found in a partially burnt condition, raising suspicion over the deaths.
The wildcats may have died five days ago.
The carcass of a female elephant was found just 50 metres from the carcasses of the tigers. Portions of its body had been consumed by wild animals.
With this, five elephants have died so far in the region in the last month. Earlier, three elephant calves and one male elephant were found dead.
Forest department personnel said the tigers may have been poisoned to death.
"A few shepherds have been venturing into the forests for grazing. The department stopped them and deployed a security guard. This may have irked them. They may have poisoned the tigers. But the reason for the elephant's death is yet to be ascertained," they said.
The viscera of the tigers have been collected and sent to the National Centre for Biological Sciences, Bengaluru, for testing.
Veterinarian Dr D N Nagaraju conducted the postmortem.
The deaths have raised many questions among conservationists and officials.
The canines and claws of the tigers were intact. There were no physical injuries to the body either.
"A few days back there was a tiger killed cattle...an agitated farmer could have poisoned the cattle. The hungry tigers could have eaten it and died," said a forest official.
This could be the first poisoning case in the last two years. The last poisoning case was in December 2014 in Karaka channel.
The tiger then had a gunshot wound. Two tiger poisoning cases were reported in 2013, one in HD Kotte territorial range and the second in DB Kuppe range in Mastigudi.