During a series of searches, officers from the police unit executed a warrant at the suburban house of ex-Montreal city manager Robert Abdallah.
The anti-corruption unit would not say Wednesday whether its officers searched Abdallah's home. But a source with knowledge of the file confirmed his residence was targeted by investigators.
Abdallah could not immediately be reached for comment.
There were no arrests as roughly 90 officers conducted raids at about 10 locations, a spokeswoman for the police unit said.
"It was just a step in an investigation where we search, we gather evidence to advance the investigation," Anne-Frederick Laurence said.
After Abdallah left his job with the city in 2006, one of Prime Minister Stephen Harper's closest aides, Dimitri Soudas, began telling Montreal's port board members he was the government's preference for president. Abdallah did not get the port position in 2007.
Abdallah has said he never found out why he was the favoured candidate and has denied allegations he was involved in corruption in Quebec's construction industry.
Former Montreal mayor Gerald Tremblay testified last year at Quebec's corruption inquiry that he fired Abdallah in 2006 when he heard of alleged improper ties with the business community.
Abdallah went on to work in the construction industry and the PMO eventually pushed for him to become head of the port.
Harper has since said the reason his government put forward Abdallah's name was that the City of Montreal wanted him there.
Mysterious telephone recordings, which surfaced in the spring of 2011, purport to capture the voices of two construction bosses discussing how Soudas could help them get Abdallah appointed to the port.
On Wednesday, the source also said investigators from the anti-corruption police force searched the homes of Frank Zampino, the former No. 2 politician in Montreal; former construction mogul Tony Accurso; and Frank Minicucci, a right-hand man of Accurso.
Zampino is facing criminal charges including fraud, conspiracy and breach of trust stemming from a City of Montreal land deal.
Minicucci, meanwhile, is facing six charges of filing false returns in an alleged tax fraud between 2005 and 2010. Accurso was slapped with more than 900 charges and at least $8.5 million in fines for alleged fraud over the same period. He pleaded not guilty last September.
Evidence presented last year at the Charbonneau Commission showed a link between Abdallah, Zampino and Accurso. The inquiry's counsel deposited photos taken of the three men in 2006 while they were on holiday together in the Grand Canyon and Las Vegas.
Other witnesses at the provincial corruption inquiry — known as the Charbonneau Commission — have discussed Abdallah in their testimony.
Former construction boss Lino Zambito has testified that Abdallah instructed him, through a middleman, to use more expensive piping from a particular firm while working on a major sewer contract.
Abdallah has denied this allegation.
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