Police said on Monday that they were seeking a 57-year-old man who is alleged to have shown his 13-year-old niece and her friend pornographic material.
The probe was launched after the two girls claimed that the man would drive them to remote areas and photograph them as well as showing them a pornographic video.
Separately, officers arrested a 44-year-old man from a Roma camp in the area of Drosero, near the northern city of Xanthi, after a 16-year-old girl who said she is his daughter claimed that he had sexually molested her.
The girl was transferred to a local hospital where medical examiners determined that she had been sexually abused.
Meanwhile, a sample of DNA was sent to a state laboratory and is to be compared to that of the 44-year-old.