The number of endangered crocodiles that have died this month in the central Indian state of Madhya Pradesh has risen to 67, officials say.
Gharials feed mainly on small fish (Photo: Ajit Patnaik)
The crocodiles, known as gharials, have been found dead of an unknown disease in the Chambal River sanctuary.
One or two are washing up every day on the river banks, causing concern among wildlife officials and organisations.
They are appealing for help and a team of international veterinarians is expected in the country soon.
Forest officials have collected water samples and conducted post-mortems on some of the reptiles.
The results have shown that the deaths are the result of disease which is still to be identified.
Last month one official said cirrhosis of the liver was the cause of the deaths. Tests were then carried out on the water for the presence of any liver-damaging toxins.
There are only about 1,500 gharials left in the wild in India. They have a distinctive long, narrow snout adapted for eating small fish,
The gharial, also known as the Indian Crocodile, is one of the longest of all living crocodilians - an adult male can approach 6m (20ft) in length.
In the 1970s, the reptile was on the brink of extinction and recently the species was reclassified, from being 'endangered' to 'critically endangered' by the World Conservation Union.