Several other such cases have been reported from Uttar Pradesh state in the last three years.

The Uttar Pradesh State Forest Minister, Rajdhari Singh, told the BBC the decision to hand over the inquiry to the Central Bureau of Investigation (CBI) was taken in a meeting with federal forest officials in Delhi.

According to the minister, the federal police will be able to enlarge the scope of the inquiry to other related areas, as it has wide jurisdiction and more resources.

Poaching gangs

The state police last week recovered seven tiger heads, one skin and 41 kg of animal bones from a village inside the Dudhwa tiger reserve forest.

Four local tribal people were also arrested in connection with the find.

Police say that a gang of poachers has been operating for the last six years and that the body of a tiger was recently recovered from outside the tiger reserve area.

Forest officials say that the skin of the tiger was removed - although most of its teeth were intact.

Forest officials suspect that the tiger might have been killed by poachers, but they have not ruled out the possibility of a natural death.

The tiger's body has been sent for post mortem to ascertain the cause of death.

The state authorities say that the Dudhwa forest - close to the border with Nepal - is being used to smuggle tiger parts to the international market.

The minister said local people help smugglers for money.

Illegal pursuit

Tigers are not the only targets of the poachers.

Recently, five elephants were killed in the famous Corbett Tiger Reserve.

The killing of tigers and other endangered species is banned in India, where the law prescribes severe punishments for those caught poaching.

It is reported that tiger parts are widely used in China, the Far East and the Gulf countries where they fetch a large amount of money.