Sources said a viscera examination had revealed the presence of a large number of unicellular protozoan microbes in the liver and kidney of the dead reptiles.

Initial IVRI test reports had pointed to the presence of heavy metals in the livers. It was then assumed that the cold had caused the deaths as the metals impaired the ghariyals’ liver functions. But latest findings have turned that theory on its head.

A team of scientists from IVRI, which visited the NCS a couple of days ago, also conducted tests on the Chambal river’s water and found nothing unusual.

IVRI head D Swaroop said a conclusive opinion could only be formed after all test reports came in. “At this point of time, we cannot say with certainty what caused the deaths as some reports are still awaited. We are also waiting reports from other laboratories.”

NCS had also sent organs of the dead ghariyals to the Industrial Toxicology Research Centre (ITRC) in Lucknow, which had confirmed the presence of heavy metals in the livers as well.

ITRC scientist and Public Relations Officer Bhaskar Bhattacharya said, “We are still conducting the tests.”