Justin Bieber’s recent brushes with the law don’t seem to have curbed his appetite for getting into trouble. On Sunday, while the19-year-old teen pop star was in Detroit for a sold-out concert, United States border agents searched his tour bus, seizing marijuana and drug paraphernalia.

According to the Detroit Free Press, the search took place when the bus tried to cross the U.S. border from Canada on the Ambassador Bridge. U.S. Customs chief officer and spokesman Kenneth Hammond told the publication in an email that Bieber was not on the bus at the time of the search. Hammond said that the amount of marijuana found, which he described as small and likely intended for personal use, was seized by officers.

The marijuana was reportedly discovered by a police dog during an inspection. Hammond said that the driver was issued a civil penalty and then released along with the other passengers. He did not offer any other details about the incident.

Although Bieber was away during the inspection, possibly preparing for his performance later that night at Detroit’s Joe Louis Arena in front of a crowd of 20,000, the incident marks the second time this year that the pop star’s tour bus has been found with illegal drugs. In a similar encounter in April, Swedish police searched Bieber’s tour bus after reportedly smelling marijuana wafting from inside of it.

The bus had been parked outside of the Grand Hotel where Bieber was staying, but police spokesman Lars Bystrom told reporters that the singer had not been onboard.

Bieber had already found himself at the center of drug rumors well before that investigation, when photos either of him, or a look-alike, smoking a joint at a party were circulated on the Internet. Bieber’s camp initially claimed the latter, blaming the suspicious photos on a Belgian doppelganger named Robin Verrecas.

Bieber eventually addressed the rumors in an appearance on NBC's "Saturday Night Live" in February, subtly acknowledging that he had been caught smoking marijuana and apologizing to fans. In a skit on the comedy show, Bieber, playing a Miley Cyrus fan, criticized Cyrus (played by "SNL" cast member Vanessa Bayer) for associating with the Canadian singer.

"You're kidding me, right? He looks like a lesbian. ... I heard he still has his baby teeth," Bieber’s character said. "I also heard he got busted for smoking weed, and he's really sorry about it, and people make mistakes, and he's never gonna do it again."

He followed up the skit with a second apology in March when he told Us Weekly, “I’m young, and I make mistakes.

"The biggest misconception about me is that I'm a bad person," he said. "I get upset about that. I have a big heart. I want to be a good role model, but some people want me to fail."