At least six gunmen stormed the depot of the private bus company, completely destroying 23 vehicles and badly damaging 11 others in the town of Osasco, some 25 kilometres outside Sao Paulo.
"They were all heavily armed. They took some employees hostage," said Miguel De Albuquerque, manager of the company, speaking to the Globo G1 news site.
"Two of the criminals, who appeared to be minors, poured oil on the buses. Since that was taking a lot of time, the others made two of our employees help them," said De Albuquerque.
Bus burning has become an increasingly common act of protest among some groups.
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TV Globo reported that 364 buses have been attacked since the beginning of the year in Sao Paulo and its suburbs, of which 115 were set ablaze.
In the past few days alone, there have been bus burnings in protest against water shortages that have hit some neighborhoods in this city of some 12 million inhabitants.
Motives for the bus burnings range from tit-for-tat drug turf battles to outrage over a long-running police operations to rid favelas of criminal elements.