MONTREAL - Frank Zampino, once the second most powerful man at city hall, was pulled out of his bed by Montreal police on Thursday at dawn.

Bernard Trepanier, Mayor Gerald Tremblay's former chief fundraiser, was also arrested as investigators working for the Surete du Quebec's permanent anti-corruption squad also swept up Martial Filion, the mayor's former chief-of-staff.

Police arrested nine people on Thursday morning, including construction magnate Paolo Catania as he boarded a plane at Pierre-Elliot-Trudeau International Airport.

With the nine in custody, accused of corruption and influence peddling, the corruption scandals that have rocked Quebec over the last four years have returned home to where they started: Montreal city hall.

The three former members of the mayor's inner circle were arrested in connection with an alleged fraud scheme related to a public contract worth over $300 million.

Even the mayor was among the 120 people questioned by police, over the course of a three-year investigation prompted by a tip. Police wouldn't say how many times they had spoken to Tremblay.

The mayor admitted to being shaken by the developments.

"These are serious arrests and I hope light will be shed on this as quickly as possible," Tremblay said. "There's no doubt that this affects the credibility of elected officials and, in this case, most acutely of municipal officials."

The raft of arrests is among the biggest against alleged corruption in a province that has been awash in scandals for several years.

Police say the arrests and subsequent charges are related to a property deal in 2008 when the City of Montreal sold a piece of land in the East End for a massive condo project, the Faubourg Contrecoeur, at far below market value.

A La Presse investigation revealed that the land was valued at $31 million dollars by the city, but was sold to Catania Construction for a fraction of that, $4.4 million.

The suspected scheme was relatively simple: municipal officials were accused of slipping privileged information, like technical specifications, to a construction company that was involved in a competition for a public contract.

Those accused of providing the details were well rewarded, according to police: "We're talking about monetary advantages and gifts," said SQ Inspector Denis Morin.

Fillion, once the mayor's chief of staff, was actually the head of the municipal agency that oversaw municipal real estate at the time the alleged crimes took place.

Charges to the group will include fraud, conspiracy and breach of trust.

Wearing a hoodie and sunglasses, Zampino was hauled out of his house in handcuffs and taken into custody Thursday morning. He was questioned for hours.

"For us, he was the brains of the operation," Morin told a packed news conference.

The SQ's anti-corruption unit, UPAC, had its first major bust last month, arresting 14 people including construction bigwig Tony Accurso. It also detained politically connected players in an alleged scheme involving kickbacks and bribes in exchange for advantages in the awarding of public-works contracts.

One provincial politician who had been vocal in demanding a public inquiry expressed satisfaction. He told reporters in Quebec City that the people being arrested were no longer minnows—but "big fish" in the political world.

Zampino, 53, had vacationed on Accurso's yacht before and after one of Accurso's companies was awarded a historically lucrative contract to install water meters as part of a consortium.

After leaving municipal politics, Zampino had gone on to work at another engineering firm that was also part of the consortium, and quit when the yacht stories came out. He maintained he had never intervened on behalf of any company.

Zampino, who was Tremblay's right-hand man, was the chair of the city's executive committee -- essentially the head of the municipal equivalent of a cabinet.

"We've said it before and will say it again: nobody is above the law," said Francois Roux, a director with the SQ.

The others charged were: Martin D'Aoust, 37; Pasquale Fedele, 48; Andre Fortin, 47; Daniel Gauthier, 54; and Pascal Patrice, 43. Construction company Frank Catania et Associes Inc., was also charged with fraud, conspiracy and breach of trust.

In 2010 the police squad raided the offices of Catania and the city of Montreal's development arm, SHDM, after a review of expenditures by independent accountant firms and the city's auditor general.

That firm was raided once again on April 25, 2012, as part of a sting operation against 11 companies.

With files from The Canadian Press.