It was found by a bus driver yesterday at Maharana Pratap bus stand, commonly known as Ballabgarh bus stand.
In the handwritten letter, LeT and another militant outfit have claimed that they will blow up the bus stand on May 5, Investigating Officer Phool Kumar said, adding, police is verifying the letter's authenticity.
An FIR has been registered at Ballabgarh police station under Section 121A (conspiracy to wage war, or attempting to wage war or abetting waging of war, against the Government of India), 507 (criminal intimidation by an anonymous communication) and other relevant sections of the IPC.