Police did not give a figure but Folha de Sao Paulo newspaper said on its website that some 20 buses were torched in a garage where unused vehicles were stored.
Another three buses were set ablaze in other parts of the mega-city.
Police did not confirm whether the fires were linked to Brazil’s 7-1 defeat to Germany in the semi-final, which knocked the national team out of the World Cup it is hosting.
“This is under investigation,” a state militarized police spokesman told AFP.
Looters ransacked an electronics store in the east of the city.
Buses are often burned by robbers or as a form of protest in Brazil.
Brazilians cried, cursed their president and covered their faces in shame after their beloved football team’s humiliating 7-1 thrashing by Germany in the World Cup semi-finals Tuesday.
After the fifth goal, well before half-time, hundreds of people left their expensive seats at the stadium in the southeastern city of Belo Horizonte.
A section of the crowd chanted obscenities against the players and President Dilma Rousseff, who during the cup had mostly enjoyed a reprieve from protests over the record $11 billion spent to host the tournament.
The tears began well before the final whistle, with the third German goal in the first half causing children and adults to start bawling in the stadium and in public screenings across the continent-sized nation.
As people streamed out, police reinforced security inside and around the stadium, but no incidents were reported.
Others around the country shouted at their televisions and abandoned public screenings as the Selecao suffered the biggest defeat of its 100-year history.
Amid the deluge of goals, a downpour only added to the already gloomy mood of thousands of fans in Brazil’s canary-yellow jersey at the official “Fan Fest” on Rio de Janeiro’s Copacabana beach.
Two dozen fans scuffled, forcing police to intervene.
But they never thought it would be this bad.
“This is a terrible match and Brazil without Neymar are terrible. I hate this match. It’s embarrassing to lose like this,” said Beth Araujo, 24, a biology student.
“The only good thing is I think it will affect President Dilma in the election. But all our politicians are even worse than the team,” she said.
Rousseff said she was “very sad” and “sorry” about the result.
– ‘Shame of Shames’ –
Brazil had hoped to exorcise the ghost of its defeat to Uruguay in the 1950 World Cup final in Rio de Janeiro, a national trauma dubbed the “Maracanazo” because it was played in the Maracana Stadium.
This time, TV commentators were talking of the “Mineirazo,” after the Mineirao Stadium, with the sports website globoesporte.com calling the defeat the “Shame of Shames.”
“The Maracanazo becomes nothing and literally a thing of the past,” the sports daily Lance said on its website.
But Jessica Santos, a 23-year-old photo student, was taking the massacre in stride.
“The cup is back in Brazil for the first time in 64 years so of course we’ll cheer until the end,” she said. “If Brazil wins, we party, if Brazil loses, we still party. It would have been worse to lose to Argentina in the final.”
At a popular night district of Sao Paulo, fans shouted insults at goalkeeper Julio Cesar and other players.
“I was afraid we would lose because we were without Neymar and Thiago Silva. But I never thought it would be a massacre,” said Alexa Rosatti, 19, a university student. “I stopped watching for a second and they already had scored a sixth goal.”