UPAC is executing four search warrants on Simard-Beaudry and Dessau construction firms.
Radio-Canada reports the investigation is regarding the awarding of contracts by the City of Laval.
So far, no arrests have been made, but witnesses are being questioned by investigators.
Some 90 police officers are involved in the raids.
Laval latest focus in corruption
Laval has been the focus of recent raids by UPAC. In the wake of allegations of corruption, Laval Mayor Gilles Vaillancourt took medical leave last week.
On Monday, the head of the city's executive committee, Basile Angelopoulos, said Vaillancourt is continuing to rest and to reflect while on leave.
On Oct. 24, anti-corruption officers raided a branch of the Desjardins credit union in Laval and seized contents from about 10 safety deposit boxes linked to Vaillancourt.
Vaillancourt's homes and offices were also raided in October as a part of ongoing investigations into corruption.
Over the past month, officials raided Laval's city hall and the engineering and human resources department offices.
Vaillancourt has denied allegations of corruption since being accused of illegally financing the provincial Liberal Party in 2002.
Premier Pauline Marois has since demanded Vaillancourt's resignation.Suggest a correction