Another four American aid workers have been flown home to the United States for monitoring following possible exposure to the deadly Ebola virus.
Tuesday's arrival brought to 15 the number of Americans flown home from Sierra Leone since Friday.
U.S. officials said the individuals would be housed near the University of Nebraska Medical Center, the National Institutes of Health in Maryland or Emory University Hospital in Atlanta. All three have been used to treat American Ebola patients in the past.
None of the returned aid workers has developed symptoms of Ebola. But they may have been exposed to the American clinician who came down with Ebola last week while working in West Africa for Partners in Health, a Boston-based international aid organization. That man is in critical condition at a National Institutes of Health hospital in Bethesda, Maryland.
The virus has killed more than 10,000 people in the West African nations of Sierra Leone, Liberia and Guinea. More than 24,600 people have been infected with Ebola since the West African outbreak began in December 2013.