A ninth child has died at a pediatric rehabilitation center in New Jersey due to an outbreak of a respiratory virus, officials announced Sunday.

The New Jersey Department of Health said in a news release that "another medically fragile child" who had a confirmed case of adenovirus at the Wanaque Center for Nursing and Rehabilitation died Saturday night. The child had become ill before Oct. 22, according to officials.

“This is a tragic situation, and our thoughts are with the families who are grieving right now,” New Jersey Health Commissioner Dr. Shereef Elnahal said in a statement. “We are working every day to ensure all infection control protocols are continuously followed and closely monitoring the situation at the facility.”

The new diagnosis brings the total number of cases at the facility to 25. A staff member at the facility also became ill as part of the outbreak but has since recovered. Another death Friday of a medically frail resident has not been confirmed by laboratory results as being linked to the illness, according to the NJDOH.

The illness, identified as adenovirus 7, poses the most significant risk to patients with weakened immune systems or existing respiratory and cardiac disease. According to the CDC, the virus causes a wide range of illnesses -- including the common cold, sore throat, bronchitis, pneumonia, diarrhea, pink eye, fever, bladder infection, inflammation of the stomach or neurologic disease.

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The most recent date of illness onset was Oct. 22, and it is believed that those sickened became ill between Sept. 26 and Oct. 22. The affected children in the facility’s pediatric ventilator unit had severely compromised immune systems, including respiratory problems, before the outbreak began, according to the agency.

“As part of an ongoing effort to ensure all infection control measures are followed, we are taking extra steps to monitor residents and staff for any signs of infectious illness,” Elnahal said. "Not all viruses are adenovirus. Often people become ill for many reasons, especially these medically fragile children who had respiratory problems as part of their underlying medical conditions.”

The facility has since stopped admitting new residents as long as the outbreak is ongoing. The outbreak won't be declared over until the center can go four weeks without patients being newly infected.

The state health department has sent a team of investigators to the facility to determine the cause of the outbreak. The CDC is also investigating the outbreak.

Fox News' Alexandria Hein and Katherine Lam contributed to this report.