Justin Bieber in bong mystery

Troubled pop star Justin Bieber is embroiled in another scandal after a member of his entourage was pictured dumping water from a marijuana pipe out of the singer's van.

The teenage singer has been spotted traveling around California in a luxury Mercedes vehicle with a group of friends this week (beg02Sep13), and a snap has appeared online showing a mystery passenger in the van holding what appears to be a bong out of the window.

The picture, obtained by TMZ.com, shows the person, whose face cannot be seen, tipping water from the pipe.

It is not known whether Bieber was present, but the van is said to have been en route to a music studio in Los Angeles, and the singer later posted an Instagram picture of himself recording. He also updated his Twitter.com followers about his time at the studio.

Bieber's wild antics have made him a regular in the headlines over the last few months. He recently faced a police investigation over allegations his entourage was involved in a nightclub fight in New York, while last week (ends01Sep13) he was allegedly embroiled in an altercation in Toronto, Canada.