The first of a group of 10 American aid workers who may have come into contact with the Ebola virus in Sierra Leone were evacuated on Saturday, American government and aid officials said. They will be the largest group of Americans to have returned home over fears of exposure to the virus since an outbreak in three West African countries was declared last year.

The 10 worked with the American charity Partners in Health and were determined to have varying degrees of risk but no symptoms, said Sheila Davis, who leads Ebola response efforts for the group, which she said would continue working in Sierra Leone. A medical worker for the charity was confirmed to have Ebola last week and returned to the United States on Friday.

Another worker with the group, who had shown signs of illness, arrived in the United States on Friday evening. She tested negative for Ebola twice, said several officials unaffiliated with the charity, speaking on the condition of anonymity. She was sent to Emory University Hospital in Atlanta, which has a specialized unit for Ebola patients. The hospital had no information to provide on the patient, an Emory spokeswoman said.