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.
Keiko Fujimori declared winner of Peru presidential race
After weeks of protests, fraud accusations and review of contested ballots in a razor-thin race, conservative Keiko Fujimori was officially declared the winner of Peru's presidential race by the country's electoral office on Friday.
Ukrainian rescuers clear rubble as Kyiv mourns 30 killed in Russian attack
Rescuers cleared the rubble in the Ukrainian capital Kyiv on Friday in a search for survivors, as flags were lowered to half mast to mark a day of mourning, a day after a Russian missile and drone attack killed at least 30 people.
Monaco blast suspect is a Ukrainian woman who fled to Germany
A Ukrainian woman is the main suspect in a bomb attack that targeted a wealthy businessman in Monaco, officials said on Friday, adding that the suspect had fled to Germany and had likely not acted alone.
Clinical trials begin for two potential Ebola treatments
The World Health Organisation (WHO) announced on Thursday the launch of clinical trials for two potential treatments for the Ebola virus in the Democratic Republic of the Congo, with the first patient enrolled in the study.
India issues notice to Telegram, Signal on concerns over usernames, source says
India has issued notices to messaging platforms Telegram and Signal asking them to explain safeguards around features that allow users to post messages without revealing their phone numbers, a government source said.
