The incident took place late last night when Bhagwan Swaroop alias Mauni Baba (40), his brother Subhash (45) and Kunwar Pal Sharma (65) were injured while preparing food in Bagichi locality, they said.
The injured were rushed to the district hospital where they died during treatment, police said.
Subhash was a witness in a murder case of one Neetu who was killed last year.