The cases against Singh and his wife were registered Aug 3. The complaint against Singh was misuse of official position and criminal misconduct when he was chief minister in 1989.

In the audio CD, Singh was heard referring to some monetary transactions on phone with former IAS officer Mahinder Lal, who is now dead. It also contained recordings of his wife, a former MP from Mandi in Himachal Pradesh.

The police sent the CD and their voice samples for analysis at the Chandigarh-based Central Forensic Science Laboratory, which said the voices of Singh and his wife matched those on the CD.