At least 42 inmates have been found dead at four prisons in the capital of Brazil's northern Amazonas state on Monday.
Authorities said the victims appeared to have been killed by "asphyxiation" and were discovered during routine inspections at the prison facilities.
Additional reinforcements have been dispatched to boost security, they added, without providing more details.
This comes a day after 15 prisoners were killed in gang clashes in the same city.
UK police arrest 12 after linking crash that killed seven to organised crime
British police investigating a car crash in northeast England over the weekend that killed seven people, including two police officers, said on Monday they had arrested 12 people in a probe into organised criminal activity linked to the incident.
Landslide at Guinea landfill kills 30, government says
A landslide at a landfill in Guinea's capital has killed 30 people, the government said on Sunday, after heavy rains overnight prompted the collapse of a massive mound of waste that engulfed nearby tents and shacks.
Ukraine wants peace but won't give in, Zelenskyy says on Independence Day
Ukraine wants peace but will not just give in to Russia at any price, President Volodymyr Zelenskyy said on Monday in a defiant speech marking Independence Day celebrations.
New Zealand to introduce bill banning social media for children under 16
New Zealand's coalition government will introduce a bill in parliament on Monday that seeks to ban children under 16 from using social media, and proposes fines of up to 10 per cent of a platform's global revenue for non-compliance.
Ukrainian drone attack kills three in Russia's Krasnodar, officials say
Three teenagers were killed and another eight people, including seven children, were wounded after drone debris hit a private childcare centre in southern Russia's Krasnodar region overnight, Russian officials said.
