According to DNA tests, the child, called Maria and aged around 4, was not related to the couple she lived with.
Maria is now being looked after by a charity. Her photo has been released to help find her family.
Officials fear the little girl may have been a victim of abduction or child trafficking.
Police are appealing internationally as the little girl looks like she might be from northern or eastern Europe.
Police raided the Roma camp, near Farsala in central Greece, on suspicion of criminal activity.
They noticed the lack of resemblance between the blonde-haired, blue-eyed little girl and her parents, and found further discrepancies when they investigated the family’s documents.
The Roma family had registered different numbers of children with different regional family registries.
The woman claimed to have given birth to six children within a 10-month period.
When questioned about how they came to have Maria, the couple gave “constantly changing claims,” Thessalia Province Police Director Vassilis Halatsis said.
The couple has been arrested on suspicion of abducting a minor.
The president of the Smile of the Child organization that is looking after the little girl, Kostas Yaaopoulos, says the child is confused and shocked by the change in her environment.
The girl was being used to beg on the streets of Larissa because she was blonde and cute, he alleged.
The case will offer fresh hope to the parents of Madeleine McCann who disappeared from a Portuguese holiday resort in May 2007.
36TMspByIOIAt least 158 people have died in Spain's worst flooding disaster in generations. On October…
Google has been fined two undecillion (a two followed by 36 zeroes) roubles by a…
Embarking on a home remodel is an exciting journey, promising enhanced comfort, increased property value,…
The US presidential candidates continued to campaign across key swing states on October 20. Footage…
Elon Musk has said he will give away $1 million a day to a registered…
India and Canada have decided to expel their top envoys along with other diplomats as…