A state prison in Calipatria, a small town of Imperial County in Southern California, has been placed under lockdown late Tuesday after more than 100 inmates involved in a riot earlier in the day that saw at least a dozen prisoners injured, authorities said.

Prison guards had to use gunfire and pepper spray to quell a melee which saw over 100 inmates participating. Fourteen individuals were injured, with 10 hospitalized in outside hospitals for injuries ranging from severe cuts to gunshot wounds.

The guards fired at least four rounds from Mini-14 semiautomatic rifles, the prison authorities said.

One of the prisoners who suffered gunshot wounds had to be airlifted to hospitals. All were expected to survive, the authorities said.

No staff members were injured in the violence. The state and county authorities are going to look into the incident, officials said.

Located about 192 km northeast of San Diego, the California State Prison opened in 1992 and is housing more than 4,100 minimum-and maximum-custody male inmates. The prison has been plagued by a number of problems including overcrowdedness, understaffing and, most of all, gang violence.

An August 2005 riot at the facility left one inmate killed, and 50 others including staff members wounded.