A five-year-old female crocodile died at Siddharth Garden and Zoo in Maharashtra's Aurangabad city, an official said on Tuesday.
A post-mortem was conducted on the reptile, which died on Monday, the official said.
The animal, which was born in the zoo in 2014, did not show any sign of illness, he said.
"We consulted veterinarians and a post-mortem was conducted. Preliminary examination revealed a blockage in the animal's kidney," zoo superintendent B S Naikwade said.
The samples necessary for investigation are taken and then last rites were performed for the reptile, he added.
"Water samples from the animal's enclosure have also been sent for testing," he added.