Police in the southeast of China are investigating after receiving information a girl aged 13 was sold into marriage by her father and then became pregnant and gave birth a year later.

According to a report in the South China Morning Post Tuesday the girl was sold in late 2019 aged 13 to a 23-year-old man.

The girl, surnamed Zhang, is a resident of Ganyu District of Lianyungang, Jiangsu, and was born in April 2006, according to her identity card, the SCMP story says. She gave birth to a boy in May last year, the report says quoting local news sources.

The birth certificate says the mother was 14 years and the father 23.

Jiangsu news media that unearthed the story said the couple have since separated and she has returned home to her father. Nevertheless, she has since remarried, they said.

Her father and her first husband, Huang Gui, have been questioned by police.

The girl's father told the online news portal Thepaper he was "not sure of" his daughter's age. "I don't know that exactly," he said.

The reports say the father accepted 66,000 yuan ($10,203) as "bride gifts" from the first husband's family.

The father then accepted another $13,605 for the second marriage, the reports said.

Family members on both sides were also rewarded with cash for their "matchmaking" roles.

"I just wanted to find a good guy for her," an aunt of the girl was quoted saying. "As her aunt, I hope she lives happily. Her own home is so poor that it has nothing to eat."

China law says men can marry from 22 and women from 20. The age of sexual consent is 14.

An official from the women's federation in Lianyungang said they would help the girl, the SCMP reported. "We are still verifying the facts. We have to check with the girl herself, her relatives and folks in her village," the official, whose name was not given, said.