According to the police, they were booked on the basis of an audio CD released by Singh's political adversary Vijai Singh Mankotia in 2007. In the CD, Singh was heard referring to some monetary transactions on the phone with former Indian Administrative Officer (IAS) officer Mahinder Lal, who is now dead. The CD also contained recordings of his wife and some industrialists.

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

Dhumal has said that the investigating agencies 'are on the job to investigate cases registered against the former chief minister.'

'We are following the legal procedure. The law will take its own course,' he has said.

Meanwhile, the police have identified two industrialists on the basis of the conversation in the CD.