São Paulo – About 200 prisoners escaped a Brazilian prison after a riot on Tuesday, authorities said, in the latest in a string of violent incidents at prisons.

The riot in the CPP III prison in Bauru, in the southern state of São Paulo, started when an inmate was discovered using a cell phone, the state Secretariat of Prison Administration told dpa.

Prisoners set fire to several mattresses during the morning rebellion, according to the state-run Agencia Brasil news agency.

The riot is the latest incident in an unprecedented escalation of violence that has shaken Brazilian jails since the beginning of the year.

More than 120 people were killed in the first weeks of 2017 in bloody brawls inside the prisons, most attributed to fights between criminal groups that are disputing the control of drug trafficking in the country.

As one of several measures to deal with the crisis, President Michel Temer recently sent federal troops to shore up prison security in several states.

Humanitarian organizations have long contended that criminal gangs control Brazilian prisons, bringing weapons and prohibited devices such as cell phones into the facility with impunity.

Brazil's prisons also suffer from severe overcrowding. More than 622 000 people are imprisoned in Brazil in facilities with a capacity of 371 000 inmates.

Brazil has the fourth largest prison population in the world behind the United States, China and Russia.