A male and a female rhino died in the Delhi zoo on April 24, 2001. The cause of their deaths is still not clear. Both the rhinos were treated for intestine blockage. 'While the female rhino was undergoing treatment for some time, the male died suddenly,' said B S Bonal, the zoo's director. Preliminary blood tests done by the Bareilly-based Indian Veterinary Research Institute ( ivri ) could not establish the presence of any poisonous substance, as claimed by S C Sharma, additional inspector-general of the Union government's wildlife department. The blockage led to the deaths of the rhinos, say the zoo's vets. Though the final report of IVRI is yet to be completed, wildlife experts suggest that the rhinos were given wrong treatment.