Jail superintendent in-charge Shivshankar Priyadarshi said the incident happened when a fight broke out between the two inmates - Putali Rai and Sujit Rai. Sujeet was injured in the incident.
"We immediately sent Sujit to Hajipur Sadar Hospital from where the doctors referred him to Patna Medical College and Hospital as his condition was critical," Priyadarshi said.
The jail official added investigations were being conducted regarding the incident on how the knife landed in jail.