An American female basketball player used forged birth documents to falsely claim she had South Korean ancestry, prosecutors have claimed.
Chelsey Lee, 26, plays in the Women's Korean Basketball League, whose teams are allowed only two foreign players.
But the KEB Hana Bank centre could be permanently banned if prosecutors can prove documents she presented are fake.
Prosecutors were asked to investigate after the Korean Olympic Committee pushed for Lee's naturalisation.
The committee had wanted to include Miami-born Lee in the South Korean team at this summer's Games in Rio after she was voted rookie of the year.
Prosecutors said the man listed as Lee's father did not exist, and the daughter of a dead South Korean woman listed as Lee's grandmother confirmed she did not have other children.
The Women's Korean Basketball League (WKBL) says it will await a court ruling over the documents before issuing any sanctions.
"The league will start discussions on how to potentially penalise Lee and the team, and also strengthen the verification process when teams sign foreign players," spokesman Kim Ilku said.
WKBL teams can each have two foreign players, who face limitations in playing minutes in each game. But foreign-born players with a South Korean parent or grandparent do not count in the quota.