A mysterious outbreak that sickened 11 people in Argentina, killing four, has been solved.
Health authorities said the illness was likely caused by Legionella, the bacteria that leads to Legionnaires' disease.
The outbreak has been contained to a health clinic in San Miguel de Tucumán, which is the capital city of Tucumán province and is located 670 miles northwest of Buenos Aires.
Minister of Health Carla Vizzotti said during a press conference Sunday that four samples -- including blood, respiratory and tissues samples -- of the deceased patients tested positive for the bacteria.
"The genome of the Legionella bacterium was detected," she told reporters. "The suspicion is that it is Legionella pneumophila."
However, she said the results are preliminary and further testing is being conducted.
Legionnaires' is a severe form of pneumonia caused by inhaling the bacteria in small droplets of water or accidentally swallowing water containing Legionella.
The disease is not contagious, but outbreaks can spread if the bacteria get into a building's water supply including in shower heads, sink faucets, hot water tanks, heaters and other plumbing systems.
Although most people recover from Legionnaires' with antibiotics, certain patients -- including those who are immunocompromised or who suffer from chronic lung diseases -- can develop complications that can be fatal.
According to the World Health Organization, the cases appeared between Aug. 18 and Aug. 25 with patients complaining of fever, muscle aches, abdominal pain and difficulty breathing along with pneumonia symptoms.
Of the 11 cases, eight were among the clinic's health workers and three were among patients. Three of the four deaths occurred among health workers.
The median age of the cases is 45 and seven are male, according to the WHO. Ten people had underlying conditions that put them at risk for severe disease, including the four deaths.
As of Sept. 3, four people remain hospitalized and three are recovering at home.
Argentinian health authorities said they are conducting contract tracing to prevent further spread of the disease. Of the contacts that have been identified so far, none have developed symptoms.
"Sporadic outbreaks of legionellosis pneumonia have been reported in Argentina before," the WHO said in a statement. "There are robust surveillance activities being implemented in the affected health facility."
The statement continued, "Nonetheless, in the absence of an identified source of Legionella bacteria, the risk of developing Legionellosis for people working or hospitalized at the same health facility is currently moderate."