Justin Bieber
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Pop star Justin Bieber had marijuana, alcohol and prescription drugs in his system, when he was arrested in Miami Beach, Fla., last week, toxicology report shows.

While the report is consistent with what the 19-year-old told police officials at the time of his arrest, the exact quantity of substances found in Bieber's system is not known. He tested negative for cocaine, opiates, meth and other drugs, the toxicology report obtained by NBC News showed.

Bieber, who was arrested on Jan. 23 for drag racing through a quiet neighborhood, and booked for driving under influence, resisting arrest without violence, and driving with an expired license, admitted to smoking pot when questioned by law enforcement officials.

"Yeah, we were smoking all night at the studio," the singer told a police officer, who said Bieber "reeked of marijuana," reports said.

At the time, the Canadian singer, who police officials described as being "excited, talkative, insulting, and cocky," also admitted to taking prescription drugs that his mother had given him.

The prescription drug was confirmed to be Xanax after the toxicology report showed the presence of Alprazolam, a key ingredient in anti-anxiety medication.

The lab results were released on Jan. 29, just hours after Bieber was booked for assaulting a limousine driver in Canada. The assault allegedly took place last month in Toronto. He is also being investigated for egging a neighbor's house.

According to CNN, Bieber is currently in Stratford, Canada, and on Thursday, his father, Jeremy, posted a picture of Bieber asleep in bed next to his half-brother.

"Safe and sound #homesweethome," Jeremy captioned the photo.