Police said that the deceased, a resident of Rewati village, has been identified as Madan Lal.
According to District Magistrate Mahendra Verma, Lal was ill for the last few days and was admitted to the prison hospital after his condition deteriorated. He died there died yesterday during treatment.
As the news spread of the undertrial's death, the inmates came out of their barracks and staged a demonstration, the DM said, adding that senior officers along with a heavy force reached the spot to control the situation.