(Reuters) - A deadly viral outbreak claimed the life of a seventh child at a New Jersey rehabilitation center, where 11 other medically fragile young patients remain hospitalized with adenovirus infections, state health officials said on Wednesday.

The outbreak at the Wanaque Center for Nursing and Rehabilitation in Haskell, New Jersey, was first reported by the New Jersey Department of Health on Tuesday with the deaths six children with compromised immune systems.

The facility, which includes a pediatric center, has been instructed not to admit new patients until the outbreak ends, the department said.

Adenoviruses frequently cause mild to severe illness with cold-like symptoms, particularly in young children. The infection can cause other illnesses, including pneumonia, diarrhea and bronchitis, the department said.

“The strain of adenovirus seen in this outbreak is associated with communal living arrangements and known to cause severe illness,” the department said in a statement.

The Wanaque Center said its pediatrics center serves newborns to 22-year-olds who are “medically fragile” and provides an individualized program for each child.

The 18 patients at the facility, located about 32 miles (50 km) northwest of New York, range in age from a toddler through young adulthood, with most under 18 years old, health department spokeswoman Nicole Kirgan said in an email on Tuesday. The department was not releasing exact ages for privacy reasons, Kirgan said.

Health officials found minor hand-washing deficiencies at the facility during visits on Tuesday and Sunday, and were working with the center on infection-control issues, the health department said.

New Jersey Governor Phil Murphy said state health officials would continue with active on-site surveillance.

“Heartbroken that several children have lost their lives in an adenovirus outbreak in Haskell,” Murphy said on Twitter on Tuesday.

The Centers for Disease Control and Prevention has been notified, the Wanaque Center said in a statement emailed by its administrator Rowena Bautista.