The Lion, named Amar, was rescued from Komal Circus at Faridabad in Haryana on July 7, 2001, the official said.
The Lion was eight years old old when he was brought to the rescue centre. He was suffering from problems related to old age and died as it was not fully responding to the treatment, BBP Executive Director N Devaraj said in a statement.
The visceral samples have been collected and sent to the Institute of Animal Health and Veterinary Biologicals (IAH & VB) for clinical examination, Devaraj said.