05/29/2007 AT 08:40 AM EDT
Though she was cited for DUI
Saturday morning, Lindsay Lohan
hardly kept a low profile over the rest of the weekend.
On Sunday the actress, 20, hit a Memorial Day pool party for 944
magazine at Hollywood's Roosevelt Hotel, where DJ pal Samantha Ronson was spinning. "She was in a great mood," says a partygoer.
Early the next morning, photo agency X17
snapped pictures of Lohan apparently asleep or passed out in the passenger seat of Ronson's car, several "30 Days" sobriety pendants hanging from the rearview mirror.
According to the New York Post
, Lohan had dropped her sunglasses and cigarettes on her way out of the hotel, then collapsed when she bent to pick them up. A bouncer had to lift her into the car.
The incident came just two days after the actress was arrested and cited for driving under the influence in Los Angeles after her Mercedes struck a curb and shrub on Sunset Boulevard around 5:30 a.m. Saturday.
Police later said they found a substance tentatively identified as "a usable amount of cocaine" in connection with the accident. Lohan was hospitalized for minor upper-chest injuries; her two passengers were not hurt.
The actress was charged with a misdemeanor, a police spokesperson said at a press conference, adding: "There is a potential for additional charges." Her tentative arraignment date is Aug. 24.
Some friends are hoping that Lohan, who checked into rehab
in January, will again seek help. "The police intervening ... could be the best thing for her," one source close to her tells PEOPLE. "I think she'll have to do a real rehab this time, and not just a Hollywood rehab."
Lohan's rep did not return calls for comment.
Reporting by MARISA LAUDADIO and JEFFREY SLONIM