Nearly a hundred escaped inmates remained at large from a state penitentiary in Brazil Tuesday after a deadly riot between rival gangs left nine prisoners dead, all of them burned and two decapitated, officials said.

The riot occurred on Monday in the Complejo de Aparecida prison in the center-west state of Goias. Another 14 inmates were wounded, one of them critically, the head of the state's prison service, Lieutenant Colonel Newton Castilho, told a news conference.

The violence broke out in a semi-open part of the penitentiary when "C-Block invaded the other wings and started brutal acts against their rivals," he said.

"There were wounded, bodies burned, and two decapitations," he said, adding that inmates set fire to a cell block.

DNA testing and dental records were to be used to identify those killed and charred.

The cause of the confrontation appeared to be "splits in the drug-trafficking crime world," Castilho said.

He added that five prison guards had been on duty for the whole facility at the time, which held 768 inmates.

When security teams swept into the prison, they found three handguns and several knives.

- Overcrowding -

A total of 242 inmates managed to escape by scaling a wall, authorities said. Dozens were quickly recaptured, but 99 remained fugitives.

Following the violence and jailbreak, authorities transferred 153 prisoners to a higher-security part of the complex, and Castilho said he had requested extra guards be brought in.

Relatives were reported to be anxious for news of the inmates, complaining of little official information.

The violent episode recalled a prison riot a year earlier in Manaus, in Brazil's Amazon region, which left 56 dead.

The country's penitentiaries often see confrontations between the two main criminal gangs, the Sao Paulo-based PCC and the Comando Vermelho from Rio de Janeiro, and their offshoots. Clashes claimed more than 100 lives last year.

Brazil has the world's third largest prison population. Official data from June 2016 showed there were more than 700,000 inmates -- more than double the capacity built to hold them.

The deadliest outbreaks of violence in Brazil's prisons in 2017 were in the Manaus facility and in the state of Roraima, where 33 people died. There were also 26 deaths in the northeastern state of Natal.

Overcrowding, rampant criminality behind bars and unhygienic conditions have made the prisons hotbeds of gang activity. In many cases, imprisoned leaders continue to direct crime outside the walls through go-betweens and smuggled cellphones.