Between the naked acrobats assaulting riders and the commute-disrupting strikes, San Francisco's BART is quickly usurping the mantle of Most Obnoxious Transit System away from far more deserving candidates such as NYC's MTA and Boston's MBTA.

And now you can add amateur porn shoot to BART's list of cons.

The Mercury News reports that BART police are investigating an "amateur pornography video" that was apparently shot on one of the system's trains in recent weeks or months.

The video, which made its way to Facebook last week, was viewed by over a million people before being pulled.

"It’s not considered a serious, violent offense, but it is something that we take seriously," Deputy Chief Ben Fairow told NBC Bay Area. "It’s also one of the crimes that’s eligible for an AB 716 prohibition order which is a new law that went into effect to prohibit certain individuals who commit certain offenses from being in or around our properties."

The time of day at which the footage was shot remains unclear, though the title of the now-removed video claimed it occurred around 10 PM.

After the "sex tape" was posted on the SFist blog, someone came forward to claim that their nephew was the cameraman, and that the video was shot "a few months ago.

"He thinks he's famous now cause it's posted on WSHH," tweeted user @RAQU3L.

[photo via AP, screengrab via Vine]