Justin Bieber, after his arrest in connection with DUI and drag racing arrest in Miami Beach last week, tested positive for both marijuana and Xanax via a urine test, Breaking Celebrity News has learned.

While authorities have yet to release results of the singer's toxicology tests officially, a police source informed Miami's NBC 6 of the ongoing development in the case, after Bieber himself told officers he'd imbibed with beer, marijuana and prescription medication prior to his Jan. 23 arrest. On Wednesday, the 19-year-old, via his lawyers, pleaded not guilty to charges of DUI, resisting arrest and driving with an expired license in Miami-Dade County.