UPAC investigators searched a high-rise unit in a luxury building near Rivière-des-Prairies in Laval's Chomedey district on Friday evening.
On Thursday, UPAC raided several buildings, including Vaillancourt's home, Laval City Hall and buildings housing the municipality's engineering and human resources departments.
The searches are related to the awarding of municipal contracts.
Westmount mayor calls for resignation
The mayor of the Montreal Island city of Westmount, Peter Trent, said Vaillancourt should step down from the provincial association of civic governments.
"When you start having police knocking on your front door, I think it's about time you know he sort of steps aside. Certainly if he's innocent, he can come back," said Trent.
Trent made the same request to Vaillancourt two years ago, when an investigative report by the CBC's Radio Canada said the Laval mayor offered illegal cash contributions to two provincial election candidates.
Vaillancourt denied those allegations and has not been found guilty of any wrongdoing.
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