Quebec's anti-corruption squad UPAC executed several search warrants across Montreal early Wednesday, including at the offices of F. Catania and Associates, a construction company.
Revenue Quebec agents joined 80 UPAC workers to carry out the 11 search warrants.
Officials declined to disclose most locations, citing a need to protect the investigation.
But UPAC workers were seen at Catania's office on the South Shore, carrying dozens of boxes to and from a rented cube van.
Very few details are available, but it appears that the raids were designed to gather evidence.
UPAC is leading the charge in the province-wide investigation probing allegations of corruption and collusion in the construction sector.