Credit: Splash News

Amber Portwood is back in trouble with the law.

Radar Online reports that the 21-year-old Teen Mom is back in jail after a judge ruled she violated her probation. (In June, she pled guilty to two counts of domestic battery after an August 2010 incident in which she was caught on camera assaulting her 3-year-old daughter Leah's father, Gary Shirley.)

The MTV reality star's brother, Shawn Portwood, tells Us Weekly that "probation officers visited [her] for a random drug test at her house and they found pills in her purse that she did not have a prescription for even although she explained that they had previously been prescribed to her. In addition she missed a court hearing and that is why she was jailed this time around."

The Madison County Sheriff's Department confirmed to E! News that Amber is indeed in their jail on a "probation violation," and said it will "will be up to the courts to decide" how long she remains there.

Shawn tells Us his sister "is distraught because she was planning to spend Christmas with her family and Gary was going to let her see Leah also."