They did not release further details about the two additional deaths.
There have been a total of 104 cases since the outbreak began last month.
The deadly bacteria grow in the stagnant water of cooling systems, spreading in little droplets through the air conditioning. Authorities have disinfected the systems in 89 local buildings and say the outbreak has been contained, though more cases could surface in the coming days.
The incubation time for legionnaires' varies from two to ten days, meaning some people may already have been infected but don't yet have symptoms, said the regional director of public health.
"I'm convinced there will be new cases and I hope none of them will result in deaths," Dr. Francois Desbiens said.
The Quebec government promised additional steps against the disease last week following criticism from Quebec City's mayor. The new measures, likely to be enacted this fall, include holding building owners legally responsible for maintaining their cooling systems.
The outbreak took a political turn on Saturday when the Charest Liberals, who have been in power for the past nine years, blamed the Parti Quebecois for not doing enough when it was in power.
Premier Jean Charest cited a 1997 report that offered recommendations to curb the spread of legionnaires' disease.
The source of the most recent outbreak in Quebec City is believed to stem from two building towers.
People with weak immune systems and heavy smokers are most at risk of catching the disease. Symptoms include persistent fever, coughing and difficulty breathing.