He added that a definitive comparison could be done "rather quickly."
Interest has popped up elsewhere
In Canada, a spokeswoman for the Royal Canadian Mounted Police said its Centre for Missing Persons and Unidentified Remains had been contacted by Interpol to aid in identifying the girl, though there was no information that she is Canadian.
"We are going through the files that we have and we are developing a list of possible children that could meet that criteria," said Sgt. Lana Prosper. "We are currently looking at an age range of about 2 to 8 years old, we don't want to exclude anybody. The files we currently have to look through number in the thousands, but they include boys as well."
Once that number has been narrowed, police will contact local authorities to assist, "if needed," she said.
Police: Couple kept changing story
Authorities released photos of the two adults charged Monday in the case -- Eleftheria Dimopoulou, 40, and Christos Salis, 39 -- in hopes that the publicity would reach someone who can provide more information about them.
Interpol said it was issuing what it calls a "blue notice" asking authorities in other nations if they have any additional information about Dimopoulou or Salis.
Police said the blond child looked nothing like the man and woman with her, and DNA testing confirmed that they were not her biological parents.
A police statement said the couple "changed repeatedly their story about how they got the child."
A government news agency said police found suspicious birth and baptism records as well as family registrations that claimed the woman had given birth to 10 children and the man was the father of four more.
"I used to see the mother, she would come to the square here to beg with the child," a man in the Larissa region told the Reuters news agency. "At one point, I had asked her how she got such a blond angel. She told me she had conceived it with a blond man."
Prejudice against the Roma
Prejudice and discrimination against the Roma are widespread in Greece and elsewhere in Europe, Amnesty International says.
Maria's case plays into old prejudices about them stealing children for forced labor.
Pardalis mentioned such a possibility, saying, "We don't have any other information if this girl was forced to work or to beg on streets."
The government news agency also raised "the possibility of the existence of a ring bringing pregnant women to Greece from Bulgaria and then taking their children for sale." The agency cited past reports that empty coffins had been found for infants who supposedly were stillborn to foreign mothers in Athens.