Borussia Dortmund defender Neven Subotic is one of four people under investigation of an alleged sexual assault.

A 21-year-old woman has filed a complaint that she was assaulted at a private party at Subotic's residence.

Subotic, a former member of the U.S. under-17 and under-20 teams, changed his eligibility allegiance to Serbia -- after failing to qualify for German citizenship -- in the wake of not being selected by U.S. Soccer for the 2007 FIFA U-20 World Cup. He was born in Banja Luka, which was part of the Yugoslav nation at the time.

Subotic, who helped Dortmund win last season's Bundesliga title, recently resumed training after sitting out two months because of facial fractures.