Slideshow ( 14 images )

RIO DE JANEIRO (Reuters) - Suspected drug gang members burned at least seven commuter buses and a tractor trailer on major highways in Rio de Janeiro on Tuesday, apparently in response to police raids in slums controlled by the criminals.

The suspects ordered all the people off the bus and truck before torching them and no one was injured, authorities said. Burning buses is a common form of protest and intimidation carried out by gangs in Brazil.

Police said that rival gangs engaged in firefights early Tuesday and officers responded.

By mid-afternoon, at least 40 suspects were detained and more than 30 guns confiscated in the Cidade Alta slum.

At least three police suffered light injuries. There was no immediate word on injuries among suspects or bystanders in the shantytown amid the fighting between gangs and police.

Violence has increased in Rio since the 2016 Olympics. Rio’s debt-laden state government does not have the funds to maintain what many security experts considered a successful police program to push gangs out of slums and setting up permanent posts to keep them out.