Public health officials have now confirmed 169 cases in all — four more than on Saturday.
But officials say the outbreak is under control.
They say the most recent cases developed over the past 10 to 15 days and are only now surfacing because of a delayed incubation period.
The source is thought to be the cooling systems of two building towers, where the deadly bacteria grow in stagnant water.
Local authorities have cleaned out the systems in over 100 buildings in the Quebec City area.
The Quebec government called a public inquiry into the outbreak last week.
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