In the letter, he informed that the surveillance material was planted in 16 key locations of his office.
The locations included the office of the Finance Minister himself, the office of his Advisor Omita Paul, the office of his Private Secretary Manoj Pant, and two conference rooms used by the Finance Minister, including the main conference hall on the ground floor of the heavily guarded North Block.
Pranab Mukherjee, who tried to urge the PM to order a probe through a letter also mentioned that no “live microphone" nor any sort of recording devices were found.
According to an investigative report published by the Indian Express, Mukherjee"s letter came three days after an unprecedented “electronic sweep" of the ministry"s VVIP chambers was conducted by a private investigators team brought in by the Central Board of Direct Taxes (CBDT). The CBDT reportedly never held such a counter-surveillance operation.
A senior Intelligence Bureau official was reported by the daily as claiming that these “adhesives" were a “sort of chewing gum" that was tested in a government forensic lab. The CBDT said that these adhesives were “planted" at critical places within the finance ministry and a closer examination discovered grooves on the surface that indicated that a few tiny devices could have been pasted and later pulled out.
Mukherjee underlined in his letter that the “serious breach" of security in his office could have “wide complications". Also, he stressed on the fact that the PM should order a secret investigation on this matter.