The voice clip also contains plans for the assassination of former Defence Secretary Gotabaya Rajapaksa.
The recent development has raised suspicion, in certain quarters, of the sincerity of the probe since there are sufficient facilities at home to test the audio clips.
It is also feared that the government is attempting to distort the evidence or to delay the investigations in to the incident by sending the audio clip abroad.
DIG Nalaka de Silva is alleged to have discussed the plot with anti-corruption activist Namal Kumara who later disclosed it to the Media.
Both, DIG de Silva and Perera, have since been grilled by the Criminal Investigation Department (CID) in connection with the issue.
DIG de Silva, who is currently on compulsory leave, has also provided a voice sample for testing to the Government Analyst. Both, the Government and the Opposition, have called for a thorough investigation into the allegations since it is of a very serious nature.