Ninety Revenue Quebec investigators are executing search warrants at various businesses seemingly controlled by businessman Tony Accurso in Laval, Saint-Eustache and Montreal.
The investigation began at 8:30 a.m. ET.
One of the buildings visited by investigators houses construction firms Simard-Beaudry and Louisbourg Construction in Laval – two companies owned by Accurso.
In January, both companies had their licenses temporarily suspended by Quebec's building authority, the Régie du bâtiment, more than a year after the construction firms pleaded guilty to tax evasion worth $4 million.
At that time, the companies were ordered to pay a total of $8 million in fines and back taxes.
Authorities confirmed they are looking for possible tax fraud, and evidence will allow them to determine if charges are warranted.
Accurso was arrested in early August on charges linked to a multimillion-dollar tax-evasion conspiracy, and was released by police the same day.
RCMP arrested Accurso along with another Quebec construction magnate, Francesco Bruno, and former Canada Revenue Agency auditor Adriano Furgiuele on the same charges, as part of the still-unwinding saga of corruption in the province's construction sector that touches all levels of government.
Accurso's name has been mentioned in testimonies during the Charbonneau commission, an inquiry currently looking into corruption allegations in Quebec's construction industry.
On Monday, Lino Zambito, the former vice-president of construction firm Infrabec, told the commission he had met with Accurso and Montreal Mob boss Vito Rizzuto to discuss issues surrounding bids on a contract.Last April, Accurso was charged with fraud, conspiracy, influence peddling, breach of trust and two counts of defrauding the government after Quebec's anti-corruption unit found out that public officials benefited from gifts and money given in exchange for favourable decisions and privileged information.