A U.S. health care worker who was admitted to the biocontainment unit at Nebraska Medicine on Sunday has been released after testing negative for Ebola, the hospital said on Thursday.

The worker is one of 17 individuals brought back to the United States from Sierra Leone after being monitored for possible exposure to the virus. All had contact with an infected co-worker in Sierra Leone who is being treated for Ebola at the National Institutes of Health biocontainment facility in Maryland. 

The person in Nebraska is one of five who are being housed near the facility in case they develop symptoms. On Sunday, one individual became ill and was transferred to the biocontainment unit, but those symptoms resolved on Monday.

The individual has returned to a housing facility near the medical center where the four other individuals are being monitored for the remainder of the 21-day Ebola incubation period.

Officials did not release any details on the health care worker.