Quebec anti-corruption agents who conducted raids today targeting the mayor of Laval were allegedly looking for evidence of tens of millions of dollars that were supposedly funnelled through offshore tax havens, Radio-Canada has learned.

The officers raided a branch of the Desjardins credit union in the suburban municipality just north of Montreal and another financial institution around midday, and seized contents from about 10 safety-deposit boxes linked to Mayor Gilles Vaillancourt, CBC's French-language news service reported.

Vaillancourt has quit his post temporarily for medical reasons, city executive committee vice-chair Basile Angelopoulos said Wednesday night.

"Following the events of the last weeks, on a personal level, it has been difficult for the mayor," Angelopoulos said.

"He has consulted with his doctor who has advised him to take a break.… In the current context, and following this recommendation, the mayor has decided to take a leave to undertake a process of reflection."

Angelopoulos said the city's executive committee will run municipal business for the time being. "The City of Laval is not in crisis, and its administration is guaranteed by the executive committee while the mayor is on leave."

One of Vaillancourt's rivals for the mayoralty in the last municipal election, Robert Bordeleau, disagreed, saying the latest round of raids targeting the mayor — the third this month —  shows something is gravely amiss.

"I don't think we're living in the same city! There's a huge crisis in Laval," Bordeleau said.

He said there have been allegations for years of nefariousness in city affairs, "and finally in the last three weeks we have all these searches, and all the allegations, coming from everywhere."

2.5% kickback alleged

Agents with Quebec's anti-corruption squad — known by its French initials, UPAC — have conducted a series of raids on the Laval mayor's homes and municipal offices since the beginning of October. Several city hall departments have also been visited by officers.

Earlier this month, former construction boss Lino Zambito testified at Quebec's ongoing corruption inquiry that Laval construction entrepreneurs were expected to give a cut worth 2.5 per cent of the value of each contract they received from the city to Vaillancourt.

Vaillancourt has been mayor of Laval, Quebec's third-largest city, since 1989. He was a city councillor before that, starting in 1973.