A prison riot in Brazil led to the prisoners taking over control of the prison as they killed four inmates, beheaded two, and held two guards hostage.

The BBC says an estimated 700 prisoners took place in the violent uprising and hostage taking. Of the four prisoners who died, inmates beheaded two and threw another two off of the prison's roof.

The riot took place in the city of Cascaval in the southern interior state of Parana, not far from the border with Paraguay. Cascaval has a population of around 270,000 people.

The riot began on the morning of Sunday, Aug. 24 when two guards were taken hostage as they served breakfast. The BBC reports that the riot's triggers were the quality of the prison's food and conditions that make basic hygiene nearly impossible. They also complained about how the prison was run.

The Guardian reports that complaints about the prison's administration include the practice strip searches, the use of shackles, and a demand for more input and discussion with the prison administration about the prison's policies.

The hygiene concern most likely has its roots in the fact that Brazil has one of the most overcrowded prison systems in the world. In a system designed to hold roughly 300,000 inmates, there are currently in excess of 500,000.

A lawyer for the prison guards' union told the BBC that the inmates were using the severed heads to wage psychological warfare on another prisoner they have detained. It is believed that gangs in the prison are capitalizing on the chaos to settle scores with rivals, which would explain the psychological torture.

The prison has been ransacked and numerous areas sent on fire. The Guardian says the prisoners even raised the flag of the First Capital Command, one of the most powerful and widespread prison gangs in Brazil.