A source told the website that the court-mandated drug test was administered last week.
If indeed Lindsay's drug test came back positive, the actress will have to serve 30 days in jail, according to the terms of her probation.
UPDATE: Lohan tweeted her own response: "Regrettably, I did in fact fail my most recent drug test and if I am asked, I am prepared to appear before Judge Fox next week as a result. Substance abuse is a disease, which unfortunately doesn't go away over night. I am working hard to overcome it and am taking positive steps. I am testing every single day and doing what I must do to prevent any mishaps in the future. This was certainly a setback for me but I am taking responsibility for my actions and I'm prepared to face the consequences. I am so thankful for the support of my fans, loved ones and immediate family, who understand that i am trying hard, but also that I am a work in progress, just as anyone else. I am keeping my faith, and I am hopeful....Thank you all!!!"