Sheriff Department spokesman Steve Whitmore says Lohan is likely to be released on Aug. 1 or 2. The projected release date reflects jail overcrowding and anticipated credits for good behavior.
The actress was booked into the Century Regional Detention Facility in the Los Angeles suburb of Lynwood at 10:11 a.m. PDT Tuesday to begin serving her 90-day sentence for probation violation in a 2007 DWI case.
Whitmore said at a news conference that the actress "has been extremely cooperative and everything has been going smoothly."
Her attorney, Shawn Chapman Holley, told reporters Tuesday, "She's scared as anyone would be. But she's resolute and she's doing it."
Lohan, 24, had turned herself in as scheduled at Los Angeles County Superior Court in Beverly Hills earlier Tuesday morning, accompanied by her mother, Dina Lohan, and younger sister Ali. Her estranged father, Michael Lohan, had arrived several minutes earlier.
Holley, who had bowed out July 6 after Lohan's sentencing, had signed back on Tuesday morning after her successor, Robert Shapiro, abruptly resigned Monday afternoon.
Wearing a sleeveless top and blue jeans, Lohan sat silently during the brief proceeding. Judge Marsha Revel changed a provision of Lohan's sentence to reduce from two days to 24 hours the time between release from jail and reporting for probation.
She also disallowed the possibilities of house arrest or work release. Lohan's sentence includes 90 days inpatient rehab following jail.
At 8:46 a.m., the actress was cuffed behind her back and escorted out a side door by four sheriff's deputies, The Associated Press reported. As she left, Michael Lohan told her, "We love you, Lindsay."
Lindsay Lohan will be housed in a "special needs" unit segregated from other prisoners "for her protection," Whitmore said. "People who have this kind of notoriety . . . are kept away from the general population."
She will have at least one hour recreation time daily outside her 12-by-8 cell, and 20 minutes per meal.
Smoking, however, is not allowed, nor will the inveterate Twitterer have access to the Internet or cell phones, People magazine reported. All personal belongings, from jewelry and medications to underwear and hair extensions, are confiscated and returned upon release.