Thiruvananthapuram: The Central Bureau of Investigation (CBI) has begun its inquiry into the 'police frame-up' that set in motion the infamous 'ISRO spy case' in 1994.

A CBI team from New Delhi called on former Indian Space Research Organization (ISRO) scientist Nambi Narayanan at his residence on Tuesday.

Last month, the CBI had filed an FIR in the Chief Judicial Magistrate (CJM) accusing five former law enforcers of "wrongful arrest, custodial torture and unjustified incarceration" of Narayanan and others.

The five are former Director General of Police Siby Mathews, his deputies KK Joshua, S Vijayan, Thampi S Durgadutt, and the then Deputy Director of Intelligence Bureau RB Sreekumar.

The 1994 case also saw the two Maldivian women booked for overstay and violation of the provisions of the Official Secrets Act.

The CBI had dismissed the case as baseless. However, the Supreme Court upheld the closure report. It ordered the CBI to prosecute the former law enforcers for wrongdoing.