Quebec's anti-corruption unit (UPAC) conducted raids Wednesday in connection to an investigation into collusion involving public contracts awarded by Hydro-Québec.

Six raids were carried out at cleaning and snow removal companies and three at residences.

About 100 police officers were involved in the operation, which took place in Montreal, Laval and Blainville.

A spokesperson for Hydro-Québec told Radio-Canada they have been collaborating with UPAC on this investigation for some time and an employee at the centre of the probe was fired in 2014.

No arrests were made during the raids.

This is the first time that contracts awarded by Hydro-Québec have been the subject of an UPAC investigation.

with files from La Presse Canadienne and Radio-Canada