07/26/2006 at 04:55 PM EDT
Lindsay Lohan was hospitalized Wednesday in Los Angeles, PEOPLE has confirmed.
The actress, who is filming the movie Georgia Rule in the area, was taken to an L.A. hospital very early Wednesday morning.
"She was overheated and dehydrated," Lohan's rep, Leslie Sloane-Zelnick told TV's The Insider, which was first to report the story. "She was filming in 105-degree weather for 12 hours."
A friend of the actress tells PEOPLE that prior to her hospitalization, Lohan was at the Chateau Marmont and then the nightclub Guy's. Confirms an observer at Guy's, "She was definitely partying. She wasn't over the top, but having a great time."
Another Lohan pal tells PEOPLE the actress has been "shooting in 120 degree weather. She told me it was hotter than when she was shooting in the Herbie (Fully Loaded) fire suit."
The 20-year-old Prairie Home Companion star spent several hours in the hospital, where she was given a Vitamin B shot. She is expected to return to the set Thursday, according her rep.
"She is fine," Sloane-Zelnick tells PEOPLE. A source close to Lohan adds that the actress is currently at her hotel resting.