Authorities in the southern Indian state of Andhra Pradesh have registered a nearly 20% fall in the number of tigers sighted in its sanctuaries.
India once had about 40,000 tigers
Wildlife officials say 122 tigers were sighted in the state's 15 sanctuaries, 24 fewer than in last year's count.
However, they said Maoist activity meant they were unable to make a proper count in at least three sanctuaries.
Official estimates put India's tiger numbers at 3,700. Conservationists say it could be less than 2,000.
Andhra Pradesh's chief wildlife warden, Hitesh Malhotra, said the population of panthers had also fallen markedly - from 263 to 203 this year.
Officials said one positive sign in the census was that 84% of the tiger paw prints found in the 2004 census were repeated this time.
But the state's principal chief conservator of forests, SK Das, said his department was concerned with the fall in the tiger population and was planning to launch an investigation into the issue soon.
Officials said the census was carried out between 9 and 17 May.
In April, Prime Minister Manmohan Singh set up a tiger task force to review the management of reserves around the country after reports that between 100 and 125 tigers were being killed by poachers each year.