Public health authorities say there have now been 165 cases since the outbreak began in mid-July.
The Quebec government ordered a public inquiry into the problem earlier this week.
The source is thought to be the cooling systems of two building towers.
The deadly bacteria grow in the stagnant water of cooling systems and spread in little droplets through air conditioning. Local authorities have disinfected the systems in more than 100 buildings and say the outbreak is now contained.
Public health officials have warned that cases of legionnaires' could still surface among those infected earlier.
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