The recovery of a skeleton from a septic tank at the official residence of Tripura Chief Minister Manik Sarkar is turning into a political issue.

The Congress has demanded he resign for a free and fair investigation and the Communist Party of India (Marxist) has indicated that the crime took place 15 years ago when a Congress minister was occupying the house.

The human skeleton was recovered on Tuesday when municipal workers were cleaning the tank. Besides a skull and nine bones of different parts of the body, a bangle was also found in the tank, indicating the skeleton was that of a woman.

Official sources refused to make any comment. Superintendent of Police (Operations) Nepal Das said, "We have sent the skeleton for a forensic investigation and nothing can be said till the report is available."

The state government has decided to refer the case to the Central Bureau of Investigation (CBI). Gautam Das, a spokesman of the CPI(M), defended the decision and said he thinks an independent investigation by the CBI would reveal the truth.

Nripen Chakraborty was the first chief minister who occupied the house in 1978 and during his time another double storey building was constructed in the same complex for the chief minister. Since then the house from where the skeleton was recovered was used as staff quarters. During the Congress coalition regime the house was used by the then Public Works Department Minister Surajit Dutta.

In 1993, when the Left Front returned to power the house was allotted to the Chief Minister Dasarath Deb but he rarely stayed there keeping the house virtually vacant. Present Chief Minister Manik Sarkar has been staying in the house since 1998.

Police said that it appears that the bones are very old but could not ascertain the age of the deceased.