Justin Bieber Toxicology Report Shows He Was On Xanax And Weed

Justin Bieber was on marijuana and Xanax at the time of his DUI arrest last week in Miami, the 19-year old's just-released toxicology report shows.

According to TMZ, the singer's "urine was tested right after he was busted for driving under the influence on January 23 ... and it shows there was THC and Alprazolam [the key ingredient in Xanax, a prescription anti-anxiety medication] in his system."

On the bright side, the report shows Bieber tested negative for cocaine, opiates, meth and other drugs.

Bieber's story is consistent with the police report in which cops say the pop star told them his mom had provided him with prescription pills and that he had been smoking weed all day in a recording studio.

Bieber has plead not guilty to the DUI charges, and is set to be arraigned on February 14.