Dudhwa Tiger Reserve authorities have pinned their hopes on Indian Veterinary Research Institute (IVRI), Bareilly to ascertain the exact cause behind the death of 25 vultures, whose carcasses were recovered from a field under Bhira range of the Dudhwa buffer zone, officials said on Thursday.

The carcasses of vultures, a protected species under the Wildlife Protection Act and categorised under critically endangered species of birds, were recovered on Tuesday.