According to this report by Birdlife International , the situation for Indian Vultures is dramatic and three species could face extinction in the wild within ten years. The population of the White-rumped Vultures Gyps bengalensis has dropped 99.9 percent since 1992. Indian Vulture Gyps indicus and Slender-billed Vultures Gyps tenuirostris have lost about 97 percent of their population. The reason is the veterinary drug diclofenac which is used to treat livestock, but kills the vultures once they feed on dead animals which where treated with the drug.

The drug is now officially banned in India, but still widely available. Sadly, the drug now also seems to be available in Africa.

Sources:
http://www.birdlife.org/news/news/2008/04/vulture_declines.html
http://www.birdlife.org/news/news/2007/10/africa_diclofenac.html