"The letter was posted in Panaji from where it came to secretariat at Porvorim," a senior police official said.
The letter was received on January 13 by State Under Secretary, (General Administration), Prashant Shirodkar, following which the Goa Anti-Terrorist Squad (ATS) launched a probe.
"The letter bore stamp of the Panaji post office. It was sent on a general address of the Government of Goa and not to any particular office," the official said.
Police stepped up security across the state after receipt of the letter.
