[Photo] A man holds a two-year-old Gharial crocodile at the Madras Crocodile Bank Trust (MCBT) in India, Tuesday, Nov. 29, 2005. MCBT was set up as a major captive breeding, research and education center for conservation of Indian crocodilian species. Credit: AP Photo/M.Lakshman

LUCKNOW, India (AP)???Conservationists and scientists scrambled Tuesday to determine what has killed at least 50 critically endangered crocodile-like reptiles in recent weeks in a river sanctuary in central India.

Everything from parasites to pollution has been blamed for the deaths of the gharials???massive reptiles that look like their crocodile relatives, but with long slender snouts. The bodies, measuring between five and 10 feet long, have been found washed up on the banks of the Chambal River since early December, according to conservationists and officials.

The precise number of gharials that have died remains unclear, with the Gharial Conservation Alliance saying 81 bodies have been found since early December, butt Chief Wildlife Warden D.N.S Suman putting the number of dead animals at 50.

Conservationists believe there are only some 1,500 gharials left in the wild, many of them in a sanctuary based along the Chambal, one of the few unpolluted Indian rivers. The Chambal contains the largest of three breeding populations in the world.

In early December, officials found the bodies of at least 21 gharials over three days. The bodies have continued washing ashore in the weeks since.

The latest possible clue to what's killing the rare reptiles is an unknown parasite that scientists found in the dead gharials' liver and kidneys, according to Dr. A.K. Sharma of the Indian Veterinary Research Institute.

"We can say that liver and kidney of these gharials were badly damaged," said Sharma. "They were swollen and bigger than their usual size."

Other believe the gharials may have gotten sick and died after eating contaminated fish from the polluted Yamuna river, which joins the Chambal in the state of Uttar Pradesh. Pathological tests confirmed lead and cadmium in the bodies of the dead gharials, said Suman, the wildlife official.

"The Chambal river has clear water free from heavy metals. The only possibility seems that these gharials might have migrated from heavily polluted Yamuna river where they might have eaten fish," said Suman.

The gharial, also known as the Indian crocodile, was on the verge of extinction in the 1970s, but a government breeding program that has released several hundred into the wild has raised their numbers.