Goa Police is yet to trace the origins of the letter which threatened to harm Prime Minister Narendra Modi and Defence Minister Manohar Parrikar.
"We are still inquiring into the origins of the letter. The inquiry is going on," Inspector General of Police (IGP) V Renganathan told PTI today.
He said security has been beefed up across the state and all precautions are being taken.
On asked whether the letter purportedly signed by ISIS, could be a prank, he said probe is underway into all aspects but the threat has been taken seriously.
The postcard letter was received last week by State Secretariat in Porvorim near here with ISIS written at the bottom.
The Anti-Terror Squad (ATS) has already began probe and the letter has been sent to all police stations across the coastal state.
Meanwhile, BJP has condemned the act. "If the threat is true then it is sending very bad signal for the country," BJP Goa spokesman Dr Wilfred Mesquita said.
Congress party has also demanded thorough investigation into the source of the letter.
"Threat letter received by Goa government should be investigated. Defence minister's weekend visits to the state without proper security in place is also posing threat to the people of Goa as he is getting vulnerable for such attacks," Congress' Goa spokesman Durgadas Kamat said.
"But the incident can also be looked at from a different angle whether this has been done deliberately by the elements who want to divert the attention of the citizens from Goa government's misdeeds on the governance front," he commented.
