Orange County health experts are investigating 12 cases of Legionnaires’ disease among people who live in or visited the Anaheim area in September. Eight of the cases involve people visiting Disneyland and one person worked at the park.

One person, who had not visited Disneyland, has died, officials said Friday.

A Disneyland official said the resort voluntarily shut down two cooling towers in a backstage area of the theme park after it found the towers had elevated levels of a bacteria that causes Legionnaires’ disease.

Jessica Good, a spokeswoman for the Orange County Health Care Agency, said in an email Friday night the agency found 12 people, ages 52 to 94, were diagnosed with Legionnaires’ disease, a type of airborne disease that causes a severe form of pneumonia to most people 50 years or older or with a weak immune system.

One of those diagnosed was a cast member but where they worked at the park was not disclosed.

Of the 12, 10 have been hospitalized, and one person died. The person who died was described as having additional health problems and did not visit the theme park, Good said.

The health care agency is investigating all the cases, but has not yet identified a common exposure source for all of them, she said.

The illness, also known as legionellosis, is an infection with symptoms of serious pneumonia and can be deadly if not treated.

Legionnaires’ disease usually results from inhaling microscopic water droplets in mist or vapor. The bacterium Legionella living in freshwater rarely causes infections, but indoors it can multiply in water systems such as hot tubs and air conditioners, according to the Mayo Clinic.

It is not spread through person-to-person contact.

In a statement, Dr. Pamela Hymel, chief medical officer for Walt Disney Parks and Resorts, said Disney was informed Oct. 27 by the county agency of Disneyland’s possible role in the Legionnaires’ disease cases in Anaheim.

“We conducted a review and learned that two cooling towers had elevated levels of Legionella bacteria,” Hymel said in the statement. “These towers were treated with chemicals that destroy the bacteria and are currently shut down.”

Hymel added that Disney has worked with the county health care agency and that “there is no longer any known risk associated with our facilities.”

“(Disney) reported having performed subsequent testing and disinfection and brought the towers back into service (Sunday),” Good said.

While the towers, in a backstage area behind the New Orleans Square train station, were initially cleared, Disney on its own took them back out of service on Tuesday. Disney is working with health officials on the status of the towers.

Good said there have been no additional Legionella cases after September and no known ongoing risk associated with this outbreak.

In May, a community pool and spa in Foothill Ranch in South Orange County was closed after two cases of Legionnaires’ disease were reported. The disease sent two people to the hospital.

Related: 5 things to know about Legionnaires’ disease