THESSALONIKI, Greece (AP) — Three Greeks and two Georgian nationals appeared in court Friday on charges of belonging to a criminal organization that allegedly sold babies for adoption.

All five denied the charges before a Thessaloniki magistrate. The two Georgian nationals are accused of being the ringleaders.

The gang allegedly recruited pregnant Bulgarian women who were destitute and willing to give up their newborns for a fee. Authorities say the group sold babies to childless Greek couples.

A total of 12 people, including a lawyer, an obstetrician and a midwife, were arrested this week in connection with the alleged illegal adoptions and the alleged sale of human eggs. Another 54 have been charged with complicity.

Police say it was one of the biggest and best-organized gangs of its kind in Europe that functioned as a "birth industry."

The gang was active since at least 2016, and its profits exceeded 500,000 euros ($550,000), police said. The investigation, assisted by Europe's Europol police agency, traced 22 sales of babies for adoption and 24 sales of human eggs.

The pregnant women were allegedly offered up to 5,000 euros (around $5,500) to sell their babies and were brought to deliver in Thessaloniki clinics. The gang arranged for the babies to be legally adopted, but charged fees of up to 28,000 euros ($30,000) for the service. Under Greek law, adoptions can't involve financial transactions.

The gang also allegedly sold human eggs from donors recruited in Greece, mainly women from Bulgaria, Georgia and Russia, according to a Europol statement.

Europol said the women were then transferred to Thessaloniki for fertility treatments to increase the number of eggs.

The police investigation was triggered by an anonymous tip-off in March.