RIO DE JANEIRO, BRAZIL - Police said Wednesday that they busted a network of fraudsters who targeted upcoming World Cup and Olympic Games projects with bid rigging scams.

Twelve people will be charged with corruption and conspiracy following a series of raids involving 120 police officers dubbed Operation Monopoly, they said.

'This is the first phase of the investigation,' said Flavio Porto, the head of a police anti-corruption unit. 'Today it was important to have found documentary proof.'

Porto alleged that the fraudsters have reaped at least 11.4 million (S$16 million) dollars - and possibly as much as 55.5 million dollars (S$77.7 million) - since 2008 by colluding on bids for government construction projects.

The way the scam allegedly worked was that a dozen different companies would bid on a project, but all but one bid would be unacceptable.

The winner would then pay kickbacks to the losing bidders, while firms that refused to join in the scheme ran into trouble with corrupt prosecutors, police said.

Porto said the network was planning to repeat the scheme in presenting bids for contracts at the 2014 World Cup in Brazil and the 2016 Olympic Games in Rio de Janeiro.