A man who is alleged to have raped a now 9-year-old girl for three years has been detained in Guangzhou's Huadu district, Guangzhou Daily reported.

But police are finding it difficult to collect evidence to bring Qin, 50, to trial as forensic doctors said the evidence remaining in the girl's clothing is too old to prove it came from Qin.

Qin was detained after the girl's mother, surnamed Liu, recently sought police help.

Liu said she and her husband did not know their daughter had been sexually violated for three years until the girl was detected to have inflammation of her genitals and other infections. Doctors told them the girl had definitely had sex.

The girl told her parents that their neighbor Qin, who operates a store, raped her many times during the past three years.

Further investigation of the case is continuing.