The Competition Bureau said criminal charges have been laid against six companies and five people accused of bid-rigging for public contracts in Montreal.

The total charges relate to 37 calls for tender for contracts worth $3.3 million, all for sewer cleaning and maintenance.

The Bureau says the companies agreed to co-ordinate their bids to pre-arrange the winners of municipal and provincial contracts.

One of the six companies, MSC Réhabilitation, pleaded guilty Tuesday to bid-rigging in 12 calls for tender.

The company was fined $75,000.

The other companies and individuals accused have yet to issue a plea.

They face fines and up to five years in jail. The Bureau began investigating the bid-rigging scheme in the summer of 2009. A few months later it got search warrants to investigate the six sites.

Officers seized thousands of documents and interviewed numerous witnesses.