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.
Netanyahu says Israel to decide which international forces in Gaza acceptable
Israeli Prime Minister Benjamin Netanyahu said on Sunday Israel would determine which foreign forces it would allow as part of a planned international force in Gaza to help secure an end to its war under US President Donald Trump's plan.
Two suspects in Louvre jewel heist case arrested in Paris
Two suspects in the brazen daylight heist of some of France's crown jewels from the Louvre were arrested in Paris on Saturday evening and are being questioned, Le Parisien newspaper reported on Sunday, citing sources close to the investigation.
Russian attack on Kyiv kills three, injures 31
Ukraine's President Volodymyr Zelenskyy called for new strong sanctions against Russia and its allies after Russian drones killed three and injured 31, including six children, in an overnight air attack on Kyiv.
PKK announces withdrawal from Turkey
The outlawed Kurdistan Workers Party (PKK) said on Sunday it was withdrawing from Turkey as part of a disarmament process it is coordinating with the government, and pressed Ankara for concrete measures to move the process along.
Israeli military says it conducted 'targeted strike' in central Gaza
Israeli forces carried out a "targeted strike" on an individual in central Gaza who was planning to attack Israeli troops, Israel's military said on Saturday.
