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.
Thousands of Australians without power as cyclone Alfred hits
Hundreds of thousands of people in Australia's Queensland state were without power on Sunday after Alfred, a downgraded tropical cyclone, brought damaging winds and heavy rains, sparking flood warnings.
Israeli airstrike kills two in southern Gaza
An Israeli airstrike killed two Palestinians in Rafah in the southern Gaza Strip on Saturday, medical sources said, as mediators pushed ahead with talks to extend a shaky 42-day ceasefire agreed in January between Israel and Hamas.
12 people injured in Toronto pub shooting
Toronto Police said early on Saturday they were searching for three male suspects in a shooting that injured at least 12 people at a pub in the Canadian city.
Cyclone Alfred downgraded as millions stay indoors
Ex-tropical cyclone Alfred lingered off the south-east Australian coast on Saturday and forecasters said Brisbane is likely to miss the worst of the storm, a relief for millions of residents in the region who have been staying indoors.
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