The Lashkar-e-Tayiba has threatened to blow up the Golden Temple, the holy Sikh shrine which is visited by thousands of visitors everyday.
The unsigned handwritten letter in Hindi was received at the Shiromani Gurdwara Prabandhak Committee headquarters on Tuesday in Amritsar, SGPC secretary Harbeant Singh confirmed on Wednesday.
Harbeant Singh said the letter which arrived by post was handed over to the senior superintendent of police S S Srivastva.
"It could be a mischief, but we are taking no chances. We are trying to ascertain the place from where the letter was posted. Adequate security measures have been taken to ensure safety of the holy shrine," the SSP said.
Harbeant Singh said the SGPC Task Force, incharge of the security of the shrine, had been alerted.
Meanwhile, additional security force personnel have been stationed around the temple complex.