The reptiles died in the waters of the Chambal river, which runs along the borders of the northern state of Uttar Pradesh and the central state of Madhya Pradesh, baffling experts as it is considered their natural habitat.
"Autopsies confirm liver cirrhosis as the cause of death," D.N.S. Suman, Uttar Pradesh’s top wildlife official, told Reuters from Etawah town on the banks of the Chambal where experts have camped to investigate the deaths.
Poisoning was not suspected as fish in the river had not died, Suman said, adding that scientists would test the water for the presence of any liver-damaging toxins.
Cirrhosis is marked by the loss of liver tissue, leading to the loss of function of the vital organ.