A man with an intellectual disability who was being treated for Legionnaire's disease at a Dublin hospital died at the weekend.
It is unclear, however, at this stage if the disease was a factor in the man's death or if he died from other causes.
A postmortem would be required to establish the exact cause of death but it was not known last night if one had been carried out.
The man was one of two people with special needs living in a long-stay unit of Stewarts Hospital in Palmerstown who were found to have contracted the disease.
The Irish Times reported the cases on Saturday and quoted the Health Service Executive (HSE) at the time as saying one of the infected persons had fully recovered and the second had "almost recovered".
It is the person who was said to have "almost recovered" who died on Saturday, according to an informed source.
The patients who contracted the disease had both physical and mental disabilities.
A spokeswoman for the HSE, which provides funding to the hospital to provide residential and day services for people of all ages with special needs, said public health specialists would be in contact with the hospital again today to see if "any issues" needed to be followed up.
On Friday the HSE said public health specialists, in conjunction with environmental health officers, had carried out a thorough investigation after the cases first came to their attention in July. Following their investigation the water systems in the hospital were "fully flushed and sanitised", she said.
Legionnaire's disease can cause a potentially fatal form of pneumonia. In 2003 an investigation found that a 61-year-old Co Waterford woman contracted the disease while a patient at Waterford Regional Hospital where the water system, particularly the hot water system, was "heavily colonised" with the Legionella bacteria.
The bacteria can grow in warm water or air-conditioning systems. People get the disease not by ingesting water, but only when they breathe in a mist or vapour (small droplets of water in the air) that has been contaminated with the bacteria.