Six inmates at the San Quentin State Prison in California tested positive for Legionnaires' disease on Sunday morning. Five of them have been sent to outside hospitals for treatment. Fifty-one others are under observation for symptoms of respiratory illness, Reuters reports.

The Legionnaires' disease scare hit San Quentin State Prison after an inmate tested positive for the disease on Thursday, prompting prison officials to carry out measures to prevent the spread of the disease. Water was shut off, including showers and toilets. The kitchen was also closed to get rid of steam and mist during cooking, and boxed meals are now being distributed to inmates, LA Times reports.

After consulting with health experts and ensuring that toilets are not the source of the disease, state prison officials allowed the use of toilets within the housing units to resume Friday afternoon. However, taps and showers are still closed.

"Secondary water sources such as bottled water and water tanks will continue to be used for consumption until it is deemed safe to resume normal water use," the California Department of Corrections and Rehabilitation (CDCR) said in a press release. The inmates are temporarily using portable showers.

San Quentin State Prison is presently not accepting new inmates because of the Legionnaires' disease scare. Visitations and volunteer programs are also stopped.

"The California Department of Corrections and Rehabilitation, along with the Marin County Public Health Department and California Correctional Health Care Services, are continuing the investigation of the source of Legionnaires' disease at San Quentin State Prison," CDCR said.

There are 3,700 inmates and 1,800 employees in the state prison.