The cash-for-vote case, which took the two Telugu speaking states of Telangana and Andhra by storm, has reached its final stage with the Anti Corruption Bureau (ACB) waiting for approval from the Telangana government.

Following the green signal, the ACB plans to ask for the voice sample of Andhra Pradesh chief minister N Chandrababu Naidu from the assembly to test if it matches with the alleged phone call between Naidu and nominated MLA Elvis Stephenson.

The cash-for-vote case came to light after Telangana TDP legislator A. Revanth Reddy was arrested by the ACB on May 31 when he was offering Rs.50 lakh to Stephenson to make him vote for the TDP-BJP candidate in the elections for the Telangana legislative council. 

ACB, which had laid a trap on a complaint by Stephenson, also arrested Revanth Reddy's aides. TRS leaders have been alleging that Naidu is the mastermind in the scam and he should be booked.

The ACB had earlier said that there were 516 telephone conversation records in Bishop Harry Sebastian, one of the accused's phone, of which 102 related to the cash-for-vote case.

However, the most important phone call was one alleged to be between Elvis Stephenson and Chandrababu Naidu.

Last week, the Telangana State Forensic Science Laboratory (TSFSL) had confirmed that the call recordings Sebastian's phone are unedited, including Naidu's call. 

The lab also said that the transcripts of the conversations made by the Anti-Corruption Bureau (ACB) are genuine.

The ACB has already obtained voice samples of Revanth Reddy , Sandra Venkata Veeraiah, Mathias Jerusalem and Sebastian and the process of voice matching is currently on.

As the case involves the CM of a neighbouring state, the probe agency is treading cautiously and waiting for a green signal from higher-ups, reports add.