The riot began Sunday afternoon and quickly escalated.
Prison authorities have refused to give any information, and it was unclear how much of the compound was under the prisoners' control.
A fire raged on the patio as evening fell, and inmates hung messages and shouted slogans from the prison's roof and windows.
Several messages claimed that prison guards had killed at least two prisoners, beating one man to death on Saturday and killing the other last week.
"No more dead," one banner read. "The guards are assassins."
The rioting prisoners also said they want longer visiting hours and the ability to see people who aren't direct family.
Soldiers and police surrounded the building, and a helicopter clattered overhead. Family members trying to find out information on those inside gathered at police cordons and clashed at least twice with security officials.
Local police as well as soldiers were sent in to help restore order.
The riot began during what are normally visiting hours, but it was unclear if any visitors were trapped inside.
