Sasha Ruseva, 35, was identified by Bulgarian media as having given birth to the girl in a Greek hospital in January 2009 and then given her up for adoption, ekathimerini.com reported Thursday.
The Bulgarian state broadcaster quoted her as saying, "I gave my child away because we were hungry."
The report said one of Ruseva's children said her mother recognized the girl when her photograph was shown on television.
Bulgarian police have arrested Ruseva, and were trying to determine whether she is the child's biological mother.
Greek officials said this week DNA from Maria didn't have a match in an international database of missing children that doesn't include reports of missing U.S. children.
Maria is in the care of The Smile of The Child charity at an undisclosed Greek hospital, officials said.
Maria was found living with a Roma couple, who first claimed to be her biological parents but later claimed they adopted her "in a non-legal way" from a Bulgarian Roma, attorney Marietta Palavrasa told ABC News.
They face charges of kidnapping a minor and falsifying documents.
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