Authorities responded to a non-911 call around 3 PM on Wednesday at the actress' home. A patrol car responded to the scene and they escorted Barton from her residence to an undisclosed location.
They are "currently assisting" the actress, the LAPD spokesperson told Access. No other individuals were involved in the incident, the spokesperson added.
Reps for Barton were not immediately available for comment.
As previously reported on AccessHollywood.com, Barton was charged in February 2008 with four criminal counts related to a DUI arrest which occurred on December 26, 2007.
Barton was been charged with one misdemeanor count of driving under the influence of alcohol or drugs, one misdemeanor count of driving with a blood alcohol level of 0.08% or higher, one count of being an unlicensed driver and one count of possession of marijuana (28.5 grams or less).
According to the Los Angeles County Sheriff's Department, deputies pulled over a vehicle, driven by Barton after they saw her car "straddling two lanes of traffic." Barton also reportedly did not signal when making a turn.
Barton was then detained and authorities say during that period they determined she was an unlicensed driver. The LA Sheriff's Department also said during their detention of the former "OC" star, Barton appeared to have driven while under the influence of alcohol.
In April 2008, the actress plead out the charges, eventually being sentenced by a Los Angeles court judge to 36 months probation, alcohol education classes and a fine.
Barton told Marie Claire's UK edition in Fall 2008 that she went to rehab quietly following the arrest to help with her case.
"I wanted to prove to the court that I would take it completely seriously, so I went to rehab to prove I was sober," she said in Marie Claire's September issue. "It really helped in getting the more serious aspects of my case dropped because, you know, that's what they want to hear; you're not an alcoholic and you don't have a problem. So I did it in the most low-key way possible – I didn't make a fuss about it and I didn't tell a lot of my friends. I just did the program and got through it."
Related Content from AccessHollywood.com:
PLAY IT NOW: Mischa Barton Arrives At The 2008 Costume Institute Gala, Part II
PLAY IT NOW: Mischa Barton's Lawyer Talks DUI Charges