Obama's black father is from Kenya and his white mother is from Kansas. It has been reported repeatedly in the past that Obama's ancestors were not slaves.
The Utah-based Ancestry.com now says a team of researchers found his mother's mixed-race family line appears to trace back to one of the first documented African slaves in the U.S.
The company says Obama could be the 11th great-grandson of an African slave in colonial Virginia.
The Ancestry.com team used DNA analysis, marriage and property records to trace Obama's maternal ancestry. The company says two years of effort hasn't established a definitive link because of gaps in family history. The White House declined comment Monday.