A mysterious lung disease is causing the deaths of gharials, an endangered species of fish-eating crocodiles possessing unusually long, narrow jaws.
Although the first dead gharial was found on November 8, the sanctuary did not raise the alarm until at least 16 dead reptiles were found washed up on the bank of the Chambal River on Wednesday.
"The post-mortem report lists liver cirrhosis and lung damage as the immediate causes of death, which might be due to fungal, bacterial or viral infection," India's Daily News and Analysis quoted wildlife officials as saying.
However, the fact that there have been no reports of the deaths of other creatures living in the river is perplexing scientists.
"If the gharials' deaths are due to infection, other species would have also been affected" said the region's chief wildlife warden, adding that the gharial might be dying due to the pollution of the river's water or fish.
There are fewer than 200 adult gharials (or gavials, as they are also known) left in the wild. They were classed as critically endangered by the World Conservation Union this year.