Video of teen diva Miley Cyrus celebrating her birthday with a bong has surfaced online:

But, sources tell TMZ, the 18-year-old popstress was not smoking marijuana. Instead, she was inhaling  salvia, a natural herb that is legal in California and has supposed hallucinogenic effects.

Says a giggly Cyrus on the video, which was reportedly shot by a pal and "stolen" from the camera, "I'm having kind of a bad trip." Then she points off camera to someone she swears looks just like her off-again/on-again boyfriend, Australian actor Liam Hemsworth. We're guessing it wasn't dad Billy Ray Cyrus.