A UN panel criticized the excessive use of incarceration against the poor in Brazil on Thursday and voiced fears that the practice may increase ahead of the World Cup and Olympics.
The United Nations working group said it was "seriously concerned with the excessive use of deprivation of liberty."
"Brazil has one of the world's largest prison populations with more than 550,000 persons in prison," it said, adding: "About 217,000 of the detainees are awaiting in pre-trial detention."
It noted that imprisonment was often imposed even when the offense was minor, such as petty non-violent theft.
The panel said human rights advocates are concerned incarceration may increase ahead of next year's football World Cup and the 2016 Rio summer Olympics.
"We were told there is a fear ahead of those two events that as Brazil tries to spruce up its image, there could be increased detentions," Chilean member Roberto Garreton told a press conference.
The panel, which was invited by the Brazilian government, blamed the problem in part on a judicial culture that sees incarceration as the first recourse, including when minors are involved.
It also noted that the number of indigenous people in the prison population had also increased by around a third in recent years.
"The vast majority are the poorest, those who cannot afford private lawyers," said panel member Vladimir Tochilovsky.
As a result of excessive incarceration, the group said, "detention facilities were usually overcrowded. In some cases, the number of detainees exceeded the capacity by 100 per cent."