The Volusia County Health Department has not specified if any of these people died from the bacterial illness.
It was reported last week that the disease was found in two people. One of them died, but investigators have not determined the cause of death.
Health officials did not say if these cases were among the three confirmed by lab tests.
The Seagarden Inn was temporarily shut down last week after two long-term guests said they contracted the disease.
Legionnaires' disease is named after a 1976 outbreak of the disease at an American Legion convention in Philadelphia and is caused by a bacteria called legionella, whose symptoms can include high fever, chills, cough, muscle aches and headaches. These usually become evident two to 14 days after exposure.
