Police suspect the thieves tunneled into the firm's building in Sao Paulo and waited until Sunday afternoon, when the final games of the national championships were played, to break in and steal more than 10 million reais ($5.7 million).
A security guard working at the firm on Sunday reported hearing loud noises but thought they were from fireworks lit by excited fans, the Globo news network's website reported Sao Paulo police as saying.
Police said the thieves rented a nearby house several months ago and painstakingly dug a 150-meter (490-foot) long tunnel, Globo reported. They disguised themselves as residents, even putting a Christmas tree in the window, it said.
Flamengo, a Rio de Janeiro club, won the championship in what was one of the most exciting finales in years, sparking huge parties in the city.
