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.
Egypt makes new proposal to restore Gaza ceasefire deal
Egypt made a new proposal last week aimed at restoring the Gaza ceasefire deal, security sources said on Monday. The proposal follows an escalation in violence after Israel resumed air and ground operations against Hamas last Tuesday, effectively ending a two-month period of relative calm.
Kremlin says Ukraine Black Sea grain deal was not fulfilled
Russia and the United States will discuss resuming a deal to ensure the safety of merchant shipping in the Black Sea, the Kremlin said on Monday, noting that what Moscow saw as key parts of an earlier agreement on the subject were never implemented.
One killed in suspected ramming attack in northern Israel
One man was killed and another wounded in a suspected attack on Sunday in northern Israel when a man rammed his vehicle into a bus stop, then stabbed another man and fired shots at passing motorists, emergency services said.
Israeli strike at Gaza hospital kills 5
An airstrike at Nasser Hospital in Gaza's Khan Younis on Sunday killed five people, including a Hamas political leader, as Israel launched an all-out air and ground campaign against Hamas.
South Korea reinstates impeached PM Han Duck-soo as acting president
South Korea's Constitutional Court reinstated Prime Minister Han Duck-soo to the post of acting president on Monday, striking down his impeachment as he pledged to focus on steering Asia's fourth-biggest economy through a US "trade war".
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