Mischa Barton may have smoked marijuana prior to her arrest for driving under the influence and possessing drugs on December 27, according to reports.
According to a source, the 21-year-old scored a 0.12 on a breathalyser test, and owned up to smoking marijuana earlier that day.
Cops also found prescription drugs in her car in an unlabeled bottle, reports TMZ.
Barton, who was also accused of driving without a valid licence, was pulled over at the corner of La Cienega and Santa Monica boulevards in Los Angeles.
According to L.A. County Sheriff's Department, the actress' vehicle was straddling two lanes of traffic and she failed to signal before making a left turn.
The former 'O.C.' star was eventually released on 10,000 dollars bail and a court hearing has been scheduled for Feb. 28.