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 snatches airman from Iran as Trump, Israel ratchet up pressure
US special forces rescued a downed airman in Iran in a complex operation that averted a potential crisis for President Donald Trump, as the war entered its sixth week with little sign of progress in diplomatic efforts for a resolution.
At least 11 killed in Israeli airstrikes in Lebanon
An Israeli airstrike on Kfarhata, a village in south Lebanon, killed seven people on Sunday, including a 4-year-old child, while another attack on the Jnah neighbourhood in Beirut killed four people and injured 39 others, Lebanon's health ministry said in a statement.
Kuwait Petroleum Corp reports damage at units after Iran drone attacks
Iranian drone attacks hit various targets in Kuwait on Sunday, with state energy company Kuwait Petroleum Corporation (KPC) reporting fires and "severe material damage" at some operating units.
Bahrain's Gulf Petrochemical says fire under control after drone attack
Bahrain's Gulf Petrochemical Industries Company said a fire at its operating units after an Iranian drone attack was brought under control, the state news agency reported on Sunday.
Oman, Iran hold talks on ensuring transit through Hormuz
Oman and Iran have held talks at the deputy foreign minister level to discuss options for ensuring the smooth transit of vessels through the Strait of Hormuz, Oman's Foreign Ministry wrote on X on Sunday.
