Police said the letter, written in Tamil, was received by the mutt authorities yesterday and it threatened that a bomb would go off inside the mutt on June 27.
The mutt authorities handed over the letter, signed by one Parisutham, to the police today.
Already police protection was given to the mutt in the wake of strong protests from various Hindu and Saivite outfits over the appointment of Nithyananda as the junior pontiff in April.
