The What A Girl Wants star was pulled over by California Highway Patrol at around 4am on Sunday morning (28 September).
According to the CHP report, she had stopped in the middle of an intersection. The CHP says she failed a field sobriety test and was suspected of being under the influence of an unknown substance.
The results of toxicology tests are pending.
Amanda was released on $15,000 bail.
The 28-year-old is still on probation relating to a car accident two years ago and a DUI arrest. As part of a plea deal, she was given three years' probation and ordered to do an alcohol education course.
A rep for Amanda has yet to comment.
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!