A clash between inmates wielding homemade knives and picks left 13 dead and another 65 injured at La Pila prison in the Mexican state of San Luis Potosi Saturday.

San Luis Potosi Gov. Fernando Toranzo said at a news conference that 22 of the wounded were in serious condition, according to the Associated Press.

A representative of the state attorney general's office, Gabriela Gonzalez Chong, characterized the conflict not as an uprising against prison authorities but as a fight between inmates, AP reported. It began at about 4:15 a.m. local time (5:15 a.m. EDT) and ended later in the morning.

Concepcion Tovar, who is in charge of the state's prison system, told reporters that at least 100 inmates participated in the riot, which she blamed on a gang that had been harassing and robbing other inmates, according to Reuters.

Nonetheless, Toranzo said the government would investigate whether prison officials played any role in the violence, AP reported.

Disputes between rival cartels and gangs frequently spill over into Mexico's prisons, where escapes, fights and riots are common, AP said.