FREETOWN, Sierra Leone — Two new cases of Ebola were reported in Nigeria on Friday, both in spouses of health workers who died after caring for the Liberian-American who brought the disease there last month.

The health minister of Nigeria, Africa’s most populous country, said more cases beyond the 14 known ones could arise, but thus far all are linked to Patrick Sawyer, a Minnesota resident who was very ill when he arrived in Lagos on a flight from Liberia and died soon after, on July 25.

The cases were the first from secondhand contact with Mr. Sawyer. Until Friday, world health officials had hoped Nigeria’s outbreak was fading.

“We are not surprised by this,” Dr. Onyebuchi Chukwu, the health minister, said in a telephone interview. “There may be a few more. All these cases are linked to the index case, so the risk is still there. Our fingers are crossed.”