It was not clear when the children died, and though the New Jersey Health Department declined to release their ages on Tuesday, it said that the 18 people stricken with the virus ranged from a toddler to a young adult and that most were under 18.
A team from the health department is at the facility and an inspection team was there Sunday, as well.
This is an ongoing outbreak investigation.
The infected children have been described as "medically fragile" with weakened or compromised immune systems.
"The New Jersey Department of Health learned last night [Tuesday] that unfortunately, another child who was hospitalized due to adenovirus passed away yesterday", New Jersey Health Department said Wednesday.
"I am confident that the steps being taken by state and local officials will minimize the impact to all those who remain at the facility, including patients and employee", Murphy said. The one behind the New Jersey outbreak is adenovirus 7, a strain that's known to cause respiratory symptoms and spread among people living in close quarters, including military recruits.
In some cases, adenoviruses can be spread through the stool of an infected person, such as while changing a diaper.
The centre helps educate "medically fragile children", according to its website.
Adenoviruses can cause a variety of illnesses on their own, but the infections are also connected to another pediatric condition in the news: acute flaccid myelitis (AFM), a polio-like illness that can cause muscle weakness, paralysis and even death.
The CDC said in an email that it is providing technical assistance to the state.
"The Wanaque Center continues to fully cooperate with these agencies and has sought out their medical guidance with respect to the virus", the facility said. The 227-bed, for-profit facility cares for children and elderly residents.
PHOTO: Wanaque Center for Nursing and Rehabilitation in Haskell, N.J, is pictured in this undated image from Google. Health officials are working with the center on infection control issues. The rehab facility is now not admitting any new patients.