Criminal charges have been laid against 13 people and 11 companies accused of fixing the price of gas in Quebec, the federal Competition Bureau said Thursday.

The suspects and companies operated in Victoriaville, Thetford Mines, Magog and Sherbrooke.

Three companies and one person pleaded guilty in Quebec Superior Court in Victoriaville on Thursday to related charges.

The companies, which included Ultramar Ltd., face up to $2 million in fines in total.

Sheridan Scott, commissioner of the Competition Bureau, announced the charges at a news conference in Montreal Thursday. (CBC)

"Today's announcement sends a clear message that the Competition Bureau will take action to stop price fixers whenever we have evidence that they have broken the law," bureau commissioner Sheridan Scott told a news conference in Montreal on Thursday.

"Price-fixing is a fraud against consumers. It deprives Canadians of the benefits of a competitive market, including a lower price and a greater choice."

The bureau alleges the gas retailers — individual operators who ran their stations under the banners of Shell, Esso, Petro-Canada and Irving oil — called each other to agree on prices.

Ultramar was fined $1.85 million, while Les Pétroles Therrien Inc., operating under the Petro-T banner, and Distributions Petrolières Therrien were fined a combined $179,000.

An Ultramar employee, Jacques Ouellet, was fined $50,000.

Scott said an "overwhelming majority" of businesses in the markets involved are accused of participating in the alleged scheme. It’s difficult to estimate how much the alleged price fixing cost consumers, she said.

The charges result from an “extensive investigation” by the bureau from 2004 to 2007 involving wiretaps, searches and informants. The probe continues, Scott said, with investigations being carried out in other parts of Canada.

Ultramar said in a statement issued Thursday that it will not challenge the charges.

People fill up at an Ultramar gas station on Thursday, in Montreal. Ultramar is being fined $1.85 million. (Paul Chiasson/Canadian Press)

"This is obviously a regrettable situation that we deplore," said Ultramar motorist sales network vice-president Christian Houle.

Consumer advocates lauded the competition bureau’s move, saying it proves what many gas buyers have suspected for years.

The charges “give a clear signal to those who will be tempted to [create] cartels not to do it,” said Charles Tanguay, a spokesman for l’Union des Consommateurs, Quebec’s consumer watchdog.

“We see that there are severe penalties, [and] there might be class-action lawsuits,” possibly launched in upcoming days, he said.

Motorists across the country have been outraged this spring as gas prices climbed to new record highs, crossing the $1.50 a litre mark in major Quebec urban centres last week.

The charges will likely fuel public anger at oil companies, which will be damaging to the industry, Tanguay said.