A battle between groups of prisoners caused at least 11 deaths and 65 injuries on Saturday, according to officials in the central Mexican state of San Luis Potosi.

The state attorney general's office said the clash began when a group of inmates, fed up with harassment by other prisoners, used homemade knives and picks to attack their rivals starting at about 4:15 a.m. (5:15 a.m. EDT; 0915 GMT) at the La Pila prison in the state capital.

Agency spokeswoman Gabriela Gonzalez Chong said nine inmates died at the prison and two more in a hospital.

Battles between drug cartels and other criminal gangs often has spilled over into prison battles in Mexico.

The National Human Rights Commission reported in 2012 that prisoners, often linked to drug gangs, effectively run the interior of many Mexican prisons.

The Zetas drug gang has been especially active in San Luis Potosi in recent years.