A six-man scuffle broke out on the A yard of Pelican Bay State Prison on Tuesday.
An inmate was treated at Sutter Coast Hospital and then returned to the prison, while the rest were treated at the prison.
A report on a radio scanner Tuesday morning near the time of the 9:50 a.m. fight stated an inmate was being transported to the hospital after being shot with a rubber bullet.
A prison official declined comment, stating only that "less than lethal force options" were used to quell the fight. There were no staff injuries.