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.
European leaders rally behind Greenland in face of renewed US threat
Leaders from major European powers rallied behind Greenland on Tuesday, saying the Arctic island belongs to its people, following a renewed threat by US President Donald Trump to take over the Danish territory.
Israel, Syria to share intelligence following US-mediated talks
Israel and Syria agreed during US-mediated talks in Paris to set up a communication mechanism to coordinate on security, intelligence and commercial issues, the three countries said in a joint statement released on Tuesday by the State Department.
Maduro opponent Machado vows to return to Venezuela, wants election
Venezuela's main opposition leader Maria Corina Machado has vowed to return home quickly, praising US President Donald Trump for toppling her enemy Nicolas Maduro and declaring her movement ready to win a free election.
Ukraine security guarantees to include binding commitments: draft Paris summit
Security guarantees for Ukraine will include 'binding commitments' to support the country 'in the case of a future armed attack by Russia in order to restore peace', a draft statement from the "Coalition of Willing" of Kyiv's allies, showed on Tuesday.
Nicolas Maduro pleads not guilty to charges of narco-terrorism
Toppled Venezuelan President Nicolas Maduro pleaded not guilty on Monday to charges of narco-terrorism after US President Donald Trump's stunning capture of him rattled world leaders and left officials in Caracas scrambling to respond.
A major national survey, released by the Ministry of Health and Prevention (MoHAP), has found large numbers of adults in the UAE are not getting enough physical activity, while obesity, high blood pressure and high cholesterol remain widespread.
The United Arab Emirates and Ethiopia have reaffirmed their strategic partnership during high-level talks focused on regional security, humanitarian crises and global cooperation.
His Highness Sheikh Hamdan bin Mohammed bin Rashid Al Maktoum, Dubai's Crown Prince and the UAE's Deputy Prime Minister and Defence Minister, has reviewed progress on the Jumeirah Beach 1 redevelopment project.
