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.
US, German scientists win Nobel medicine prize for work on light and brain
American Karl Deisseroth and Germans Peter Hegemann and Georg Nagel won the 2026 Nobel Prize in Physiology or Medicine on Monday for developing optogenetics, a technique that uses light to control individual nerve cells in the brain.
Nigeria military aircraft crashes with 32 aboard
A Nigerian military plane flying from Benin City to Lagos crashed on Monday in southwestern Ondo state, killing 25 passengers and seven crew members.
At least 22 dead after boats collide on Congo river
At least 22 people have died after two boats collided on the Congo River in the Democratic Republic of Congo.
Spanish PM Sanchez calls snap election for November 29
Spanish Prime Minister Pedro Sanchez called an early election for November 29 on Monday, in a bid to strengthen his mandate after a fragmented parliament rejected the government's key housing decrees last week amid widespread protests.
Hundreds of French schools stay closed ahead of nationwide day of student protests
Hundreds of French high schools will begin a second week of closures on Monday as protests over dilapidated schools and classrooms, overcrowding and teacher shortages precede a nationwide day of demonstrations on Tuesday.
