Rajeev Kumar was part of the team probing the Saradha scam.

The Central Bureau of Investigation today approached the Supreme Court challenging protection of arrest granted to former Kolkata top cop Rajeev Kumar in the multi-crore Saradha chit fund scam case.

The CBI has filed an appeal in the top court against the Calcutta High Court order that had granted him relief , saying it was not an appropriate case for custodial interrogation.

The Saradha group of companies allegedly duped lakhs of people to the tune of Rs 2,500 crore, promising higher rates of return on their investments.

Rajeev Kumar was part of the Special Investigation Team (SIT) set up by the West Bengal government for probing the scam before the Supreme Court handed over the case to the CBI in 2014, along with other chit fund cases.

The Saradha chit fund scam was uncovered in 2013 during Rajeev Kumar's tenure as the Bidhannagar Police commissioner.

The high court order had said if Rajeev Kumar was arrested by the CBI in connection with the case, he would have to be released immediately on bail by an appropriate court on two sureties of Rs 50,000 each.

Observing that Rajeev Kumar had cooperated with the CBI in the probe, the high court had said it was not an appropriate case for his custodial interrogation.

It had directed Kumar, who is currently the Additional Director General of the West Bengal Criminal Investigation Department (CID), to cooperate with investigating officers.

It had also directed him to make himself available before the investigating officers in the case for questioning on a 48-hour prior notice by the CBI.

On September 21, a pre-arrest bail plea of the IPS officer was rejected by the Alipore District and Sessions Court.

The CBI has issued multiple notices to Rajeev Kumar since May 27, asking him to appear before it for questioning as a witness in the Saradha chit fund scam.

In January, the Centre and the West Bengal government were locked in an unprecedented standoff after a CBI team had reached Rajeev Kumar's official residence for questioning him but had to retreat as the local police detained its officers.

Chief Minister Mamata Banerjee had come out in Rajeev Kumar's defence and started a sit-in protest against the Centre's move.

The Supreme Court had, on February 5, stoppe the CBI from taking any coercive action against Rajeev Kumar and directed him to cooperate with the agency for questioning at a "neutral place". He was then questioned by CBI for nearly 40 hours over five days at its office in Shillong in February.