The alert could result in another appearance by Lohan before a judge whose patience has worn thin with the actress for repeated missteps during her probation. Judge Marsha Revel and Lohan's attorney Shawn Chapman Holly were to meet in the judge's chambers Tuesday afternoon.
It remained unclear why the bracelet went off. The source, who was not authorized to speak publicly, told The Associated Press that Los Angeles Superior Court Marsha Revel would receive a report on the alert soon.
Chapman Holley, said she was looking into whether a violation may have occurred. The bracelet is designed to test the skin for alcohol every half hour by sampling a person's perspiration.
Lohan has been required to wear an alcohol monitor since May 24, when she appeared before Revel days after missing a court hearing. The "Mean Girls" star is due back in court on July 6 when the judge will decide whether Lohan, 23, violated her probation because of her missed appearance.
A violation could result in Lohan being sent to jail.
Revel refused to ease Lohan's drug and alcohol testing restrictions at the May hearing and ordered the starlet to wear the alcohol monitor.
Deputy District Attorney Danette Meyers, who is handling Lohan's case, said she was aware of "an issue" that would come to the court's attention, but did not have further details.
Lohan appeared at the MTV awards show on Sunday. She also attended at least one of the show's after-parties.
She covered up the ankle monitor on the show's red carpet by wearing long pants.
The actress has been on probation since August 2007 after pleading guilty to misdemeanor drug charges and no contest to three driving charges.
Despite spending 84 minutes in jail and performing mandatory service at the county morgue, Lohan has repeatedly struggled with the terms of her sentence. In October, a judge extended her probation for another year but Meyers warned the actress she was facing jail time if she violated her probation.
The extension was the third time Lohan escaped punishment after her alcohol-education program notified the court the actress had violated its rules. Two of the instances were described as misunderstandings; the third was chalked up to a busy work schedule.
Chapman Holley said Lohan missed the hearing last month because her passport had been stolen while the actress was at the Cannes Film Festival.
