One of the latest victims is recovering in hospital and the other is responding well to treatment at home, health officials said.
All of the previously infected people have since recovered.
The two new cases were announced by NHS Greater Glasgow and Clyde following a meeting of an outbreak control team.
All 10 cases have a direct or indirect link to the Renfrew area and investigations into the source of the disease have been focused on the town.
The first five patients diagnosed were treated in hospital, while the other three were treated at home.
Legionnaires’ disease is an uncommon but serious form of pneumonia, caused by bacteria distributed widely in natural and artificial water supplies. Symptoms are headache, fever, dry cough, breathing difficulties, stomach pains and diarrhoea.
The Legionella bacteria is spread through aerosols produced from water such as water cooling towers, air conditioning units and showers.
As a precaution, all active water cooling towers in Renfrew have been treated with chemicals that kill Legionella and several towers have been sampled for the disease.
The bacteria cannot be spread from person to person or contracted by drinking contaminated water.
People in and around the Renfrew area are being advised that they can drink water and prepare food in the normal way.
The health board, which is not disclosing whether the latest patients are male or female, said its public health protection unit is working with the Health and Safety Executive, Health Protection Scotland, Renfrewshire Council and other local authorities to identify a possible source for the disease.
Dr Gillian Penrice, consultant in public health, said: “We have notified all community GPs and our frontline hospital teams to keep this outbreak uppermost in their minds when dealing with patients displaying symptoms of headache, fever, dry cough, breathing difficulties, stomach pains and diarrhoea.”
Anyone who has symptoms of Legionnaires’ disease is urged to contact their GP or call NHS 24 on 08454 242 424.
A report out last month revealed that dealing with an outbreak of the disease in Edinburgh last year cost the health service almost three-quarters of a million pounds.
Four people died after catching the disease during that outbreak, with 45 people requiring hospital care.