(CNN)Operating rooms and other areas at Seattle Children's Hospital were shut down for the second time this year due to mold problems, according to the hospital.
In a statement, the hospital said routine air tests revealed Aspergillus contamination Sunday "in three of our operating rooms and two procedural areas."
Aspergillus is a common mold that most people breathe without getting sick but that poses a greater risk to those with weakened immune systems or lung disease, according to the US Centers for Disease Control and Prevention. Health problems can include allergic reactions, lung infections and other organ infections.
Several operating room at the hospital closed in May after a similar contamination led to the death of one patient and the illness of five others in the previous months, hospital officials said.
"The rooms in which Aspergillus was detected have been closed and out of an abundance of caution, we are only performing emergent surgeries in the operating rooms that have advanced in-room filtration," the hospital said of the latest contamination. "Some surgical cases may be postponed or diverted to other local hospitals."
The hospital said the rooms will remain closed as it investigates the air-handling system.
"The precise timing and duration of the operating room closures is still being determined," the statement said.
The Washington state Department of Health said it was notified of the discovery of the mold.
"We're learning more details about the situation ... and will provide information on our actions as we move forward," DOH spokeswoman Julie Graham said in a statement.
In May, the hospital shuttered several operating rooms after air tests showed Aspergillus contamination. The rooms reopened in July.
Air filtration gaps were believed to have played a role in the presence of mold, the hospital said at the time. Outside industrial hygienists helped clear the rooms of contamination.
Mold played a part in five deaths between 2014 and 2016 at two University of Pittsburgh Medical Center hospitals, according to a 2017 report. Those patients were exposed to Mucor and Rhizopus mold.
Those who died of the infection were transplant patients. Both the hospital and the facility that handled the hospital's linens tested positive for mold, the report showed.