Police in Georgia are investigating the possibility Bobbi Kristina Brown, who remains comatose and is breathing on a ventilator, may have been the victim of foul play, TMZ reported.

Brown is the 21-year-old daughter of R&B singer Bobby Brown and the late recording artist Whitney Houston.

Investigators are focusing on her boyfriend Nick Gordon, with whom she reportedly had a history of violence.

TMZ cited unnamed law-enforcement sources as saying Brown sustained unspecified injuries and may have been involved in an altercation shortly before she was discovered by Gordon's friend Max Lomas, facedown and unresponsive in the bathtub of her home last weekend.

There has been no official public statement from Brown's family or the authorities about the circumstances that led to her medical emergency, and no arrests have been made in connection with the incident.

Houston reportedly considered Gordon her unofficially adopted son. Although Gordon and Brown referred to themselves as spouses, an attorney for Brown's father recently clarified they were never married.

Hoston accidentally drowned in her hotel bathtub while intoxicated Feb. 11, 2012. She was 48.