CNN reported as many as 2,080 inmates from two of the facility's three buildings began fighting in the prison yard late Saturday afternoon.
Officials said they do not know what prompted the riots. Police said three inmates were hospitalized, including one with a severed finger.
"We do not have anything in control," one guard told KVIA-TV, El Paso, Texas. "Everything is out of control."
The officer said a medical dispute between inmates and staff may have sparked the riot, the second disturbance at the privately-run prison in two months.
The 2,400-bed, low-security facility is operated by Geo Group Inc., CNN said. Many of the inmates are federal prisoners.