At least 34 people were killed - many burnt or horribly mutilated - in a rebellion at a prison in Rio de Janeiro, police and legislators say.
Rebel inmates demanded different gang members be held separately
The rebellion has now ended, but police said they were still securing the Benfica facility in northern Rio, and feared more bodies could be found.
The revolt began on Saturday morning when inmates seized guns and hostages during an attempt to stage a jailbreak.
A guard was shot dead by inmates when he tried to escape on Sunday.
'Bodies in the rubbish'
Rio state legislator Geraldo Moreira, who entered the prison with police after the revolt ended, said he counted 28 bodies before giving up.
"There are bodies which have been mutilated, burnt, pieces spread around, bits of bodies in the rubbish.
"I reached the point where I didn't have enough stomach to continue," he said.
Remains of at least 34 bodies have been retrieved, but firefighters said the final death toll could reach 50, the AFP news agency reported. The condition of the bodies meant identification of the dead was difficult.
The slaughter appears to have begun when members of the notorious Red Command drug gang turned on members of the Friend of Friends and Third Command gangs.
It happened after a Catholic pastor helping to negotiate an end to the revolt agreed to inmates' demands that members of different gangs be housed in separate quarters.
Relatives of prisoners have been waiting anxiously for news
A factor in many rebellions in Brazilian jails is identified as overcrowding. Benfica, however, only opened recently and was holding 900 prisoners with capacity for some 1,300.
Some government officials are reported to have complained that the jail was badly planned and constructed, however.
The 62-hour revolt began when inmates seized weapons attempted to stage a mass jailbreak on Saturday morning.
At least 14 prisoners escaped before police arrived to quash the rebellion. Police say three were later recaptured.
During the clashes, 26 guards and prison staffers were taken hostage. Five hostages were later freed to receive hospital treatment.
On Sunday, 43-year-old guard Marco Antonio Borgatte was shot in the back as he tried to escape. He died from his injuries on the way to hospital.
There are no reports that any other hostages were badly hurt, though some were suffering hunger and dehydration when they were released on Monday.
The scores of deaths at Benfica make it the worst single prison disaster in Brazil since 1992, when police stormed Carandiru prison in Sao Paulo, killing 111 inmates.