Actress Mischa Barton was arrested and briefly jailed on Thursday on suspicion of drunken driving, marijuana possession and driving without a licence.
The 21-year-old star was pulled over while driving in West Hollywood at around 3am.
Police said the actress' vehicle was straddling two lanes of traffic and that she failed to signal when making a turn.
The official police statement said: "During Ms Barton's detention, it was determined that she was an unlicensed driver and was driving while under the influence of an alcoholic beverage."
Sergeant John Hocking said that Barton was also suspected to be in possession of marijuana and an unidentified controlled substance.
Barton spent a few hours in jail before being released on $10,000 bail; a court hearing has been scheduled for 28 February.
Barton's new film, 'Closing the Ring', opens in Irish cinemas on Friday 28 December.
