Rosie O'Donnell -- Daughter Missing ... Cops Called

Rosie O'Donnell's 17-year-old daughter has gone missing, but we've learned this is not foul play.

Sources close to Rosie tell us, Chelsea ran away from home August 11 with her dog Bear.

Rosie says it's becoming a serious situation because Chelsea "stopped taking her medicine and is in need of medical attention."

A rep for Rosie tells TMZ, "Chelsea, like millions of people, lives with mental illness. It has been a difficult road for Chelsea and her family and they just want her back safe."

Rosie has called police, who we're told are investigating.

Rosie has reached out to Chelsea through her Twitter account.