The "Smile of the Child" charity, which is caring for the girl, said it had received more than 8,000 calls and thousands of emails - some with details and photographs of missing children - from people in the United States, Scandinavia, other parts of Europe, Australia and South Africa.
"The case has touched a chord with lots of people from many countries," Panayiotis Pardalis, a spokesman for the charity, told The Associated Press. "This case is now giving hope to parents of missing children."
He said the charity had forwarded all tips to the police but most people were just conveying their concern.
A dental examination showed the child is older than previously thought, 5-6 years old instead of four, the charity said.
Interpol, the international police agency, has 38 girls younger than 6 on its missing persons database but none of them reportedly fit the mystery girl's description.
The story has resonated strongly in Britain, where the tabloid press drew parallels with missing girl Madeleine McCann, who disappeared at age three from a Portuguese resort six years ago. The mother of Ben Needham, a British boy missing in Greece since 1991, said she was thrilled by the news of the girl's recovery. Her toddler was 21 months old when he vanished on the island of Kos.
Police allege the woman who was detained claimed to have given birth to six children in less than 10 months, and 10 of the 14 children the couple had registered as their own are unaccounted for. It is not clear whether the 10 children are real or were made up to cheat the Greek welfare system.
Police say the two suspects received about €2,500 a month in subsidies from three different cities.
Police have raided dozens of Gypsy settlements across Greece in the last few weeks, including four more camps Monday in Athens and Thessaloniki.
- AP