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.
Trump says deal reached to disarm Hamas, Israeli support for plan remains uncertain
US President Donald Trump said talks in Cairo between mediators and Hamas leaders on Thursday have led to a phased disarmament agreement in Gaza.
Kuwait says Iranian attack hits Chinese company building, kills one
Kuwait's Ministry of Defence said an Iranian attack targeted a building belonging to a Chinese company in the north of the country on Thursday, killing one worker and causing extensive material damage to the facility.
Japan quake snarls auto and chip supply chains as toll hits 34
A powerful earthquake that struck southern Japan this week has exposed the vulnerability of the country's manufacturing supply chains, a decade after a devastating quake in the same region triggered widespread industry disruption.
Indian federal police file charges against 13 over exam paper leaks
India's Central Bureau of Investigation has filed charges against 13 people in connection with leaked question papers for the national medical college entrance test, days after youth-led protests over the scandal forced the education minister to quit.
The UAE has strongly condemned the drone attack targeting two vessels at Damietta Port in Egypt on Wednesday.
Motorists in the United Arab Emirates will be paying more at the pump in August, the UAE Fuel Price Committee confirmed on Friday.
President His Highness Sheikh Mohamed bin Zayed Al Nahyan has directed scholarships for Serbian students to study at UAE universities.
