Officials say a labeling error caused a person infected with the novel coronavirus to be mistakenly released from a hospital and returned to a San Diego military base.
That's where more than 200 evacuees from China are living under federal quarantine.
The CDC issued a negative finding Sunday on a large batch of specimens. Among those tested were three people who had been hospitalized with symptoms and released.
On Monday, authorities discovered that one of them had tested positive and that patient was sent back to a hospital.
The agency says it will now assign a laboratory specialist to prevent incorrect labeling.