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.
Kenya tourist helicopter crash kills seven
Seven people, including five Americans, were killed on Wednesday when the tourist helicopter they were flying in crashed in Kenya's Samburu county.
US, South Korea to cut length, scope of military drills after Trump order
South Korea and the United States will cut short annual joint military drills to five days from 11 and scale back some field training, the allies said on Wednesday, after President Donald Trump ordered a substantial reduction in US participation.
Central African Republic gold mine collapse kills at least 100
At least 100 people were killed when a low-tech artisanal gold mine collapsed in the Central African Republic on Tuesday, a senior official at a local mining association said.
Israeli airstrike kills nine Palestinians at Gaza police station
An Israeli airstrike killed nine Palestinians at a police station in Gaza on Wednesday, medics said, two days after US envoy Jared Kushner ended a trip to the region that failed to push forward Donald Trump's plan to end the war in the enclave.
Thai schools hold shooting response drills after deadly school attack
Thai schools conducted active shooter drills on Wednesday, as authorities moved to strengthen security measures two weeks after a 14-year-old opened fire at a school and killed at least eight people.
