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.
Some UK departing flights disrupted by NATS technical issue
Some departing flights at major British airports were disrupted on Tuesday after air traffic control provider NATS experienced a technical issue, with Heathrow, Gatwick, Manchester and Stansted among the airports affected by restrictions and delays.
At least 73 injured after Houthi rebels attack Saudi civilian and energy facilities
At least 73 civilians have been injured after Yemen's Houthi rebels attacked a number of civilian and energy facilities in Saudi Arabia's southern region on Tuesday, state media confirmed.
Suspect detained after sabotage attacks on Germany power grid
German police have detained a 48-year-old man suspected of carrying out a series of sabotage attacks on the country's electricity grid, police and prosecutors said on Tuesday.
Nepal rescue focused on workers trapped in three tunnels
Rescuers in Nepal are focusing on three hydropower project tunnels where they believe dozens of workers could be trapped, authorities said on Tuesday, two weeks after a devastating flood killed hundreds and left thousands missing.
Indonesia reopens Jakarta airport, four others after Anak Krakatau ash clears
Indonesia has reopened its main airport in Jakarta and four others that had been closed due to volcanic ash from a series of eruptions at Mount Anak Krakatau, transport minister Dudy Purwagandhi said in a statement on Tuesday.
