RIO DE JANEIRO (AP) — A few hundred national Brazilian security forces are patrolling parts of Rio de Janeiro following a surge in violence.

The troops began patrols along busy thoroughfares in northern Rio on Monday. Many were also positioning themselves at the entrances to several favelas, or slums.

The patrols are expected to last 90 days, and could be extended.

Military police, civil police and firefighters from other states make up the force.

The deployment of national security forces in Rio follows a jump in violence in Rio, which hosted the 2016 Summer Olympics.

Several public buses and cargo trucks have been burned in recent weeks. There has also been an increase in violence in large slums like Alemao.