Pittsburgh's UPMC Presbyterian Hospital is pursuing an investigation that involves the death of two patients who may have contacted a mold infection in the cardiothoracic intensive care unit (ICU).

One of the patients, who just had a lung transplant, is battling a mold infection in his lung tissue while less than 20 ICU patients have been transferred to other units.

UPMC Presbyterian Hospital officials announced that two patients who stayed in the unit died of fungal infections. The first one had mold infection on his left leg that doctors found in October 2014. Doctors found mold on the buttocks of the second patient in June 2015. Both patients stayed in the unit and died of the infection but the type of mold contacted by the lung transplant patient is different from the first two.

The two previous patients' records were reviewed and UPMC Quality Control Chief Tami Minnier said their infections started last year. Hospital officials are still investigating whether the mold infections caused the death or played a role in the demise of the two patients in the unit. UPMC officials said the mold was found inside the wall of a room in the ICU, where the two previous patients and the lung transplant patient occupied.

Minnier added that in the previous year, around 56 patients stayed in the cardiothoracic intensive care unit. The investigation did not yield any other infections in the unit and other parts of the hospital.

"Although the role that the mold may have played in their deaths cannot be definitively determined," said Minnier. "We have notified their families of the suspected link to the mold in our CTICU."

UPMC Presbyterian Hospital's official statement said that common fungi can cause infections and this type is found on plants. One best example of its effect is when strawberries go bad. The statement stresses that most people show no reaction when exposed to molds. Patients with poor or weak immune system caused by conditions such as immunosuppression, which happens when under certain medications or after a transplant, have the highest risk of getting infected.

The hospital's official statement does not include a date for the ICU's reopening.