SAN QUENTIN (CBS SF) — Six San Quentin prison inmates have been diagnosed with Legionnaires disease as of Sunday, officials with the California Department of Corrections and Rehabilitation announced.

The first confirmed case of the disease at the prison in Marin County was on Wednesday and Sunday prison officials announced the five additional cases.

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The source of the disease is still under investigation, according to the CDCR.

Legionnaires disease is a form of pneumonia from bacteria, according to the U.S. National Library of Medicine. The disease is spread through water mist that contains the bacteria, the library’s website says.

As a result, prison officials said they have limited the use of water at the prison.

Inmates are eating boxed meals and taking showers in portable shower units. Prison officials have had bottled water and water tanks delivered to keep inmates hydrated.

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Inmates are able to use plumbed toilets after prison officials consulted with experts at the local, state and federal level.

Prison officials are also talking with the Men’s Advisory Council, an inmate group that advises the warden and other prison staff, CDCR officials said.

About 51 more inmates are being observed for respiratory illness in the prison’s medical unit, none of which have been diagnosed with Legionnaires disease.

All volunteers programs and family visiting has been cancelled, CDCR officials said. New inmate intake has also been halted at the prison, which serves as a reception center for new inmates to California’s prison system, according to CDCR officials.

About 3,700 inmates live at San Quentin and the prison has about 1,800 employees, CDCR officials said.

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