Image copyright Google Maps Image caption The outbreak occurred at the Wanaque Center

The death toll from a viral outbreak at a medical care centre in the US state of New Jersey has risen to seven children, with 11 more infected.

The strain of adenovirus at the Wanaque Center for Nursing and Rehabilitation was "associated with communal living" and "known to cause severe illness", officials said in a statement.

The children affected were "medically fragile", the statement added.

The state investigation is ongoing. The centre is now closed to new patients.

The health facility in Haskell is privately owned. The centre did not immediately respond to a request for comment from the BBC.

According to an earlier Department of Health release, state officials began investigating on Sunday and continued on Tuesday.

On Sunday, an inspection team found "minor handwashing deficiencies" at the centre, which also provides short- and long-term adult nursing and rehabilitation services.

It is still unclear how and when exactly the outbreak began.

Local news site NewJersey.com reported that a letter had been sent to parents of patients about an outbreak on 18 October, but officials did not confirm any details about the virus until Tuesday.

The state health department said it was working with the Wanaque Center "to ensure that all infection control measures are being followed". It said the Centers for Disease Control (CDC) was helping with its investigation.

Children in the centre's paediatric ward are seriously ill - many are disabled, in comas, or cannot walk or speak, the North Jersey Record reported.

The children affected have not been identified.

Image copyright Smith Collection/Gado Image caption A colourised TEM (transmission electron microscopic) image of adenovirus

What is an adenovirus?

Adenoviruses are a type of virus usually spread through close contact (like touching an infected surface or shaking hands), coughing, and sneezing, according to the CDC.

Different strains of adenoviruses can cause a range of illnesses, including common cold symptoms, bronchitis, pneumonia and diarrhoea.

Serious complications are uncommon, but the CDC notes those with "weakened immune systems, or existing respiratory or cardiac disease" are at a higher risk of severe sickness from adenovirus infections.

Officials say the strain affecting children at the clinic, number seven, is associated with communal living and "can be more severe".