An unknown number of posters slapped up on BART trains began surfacing on Friday telling racists to "get their s--- together," but are not approved by the transit agency.

The poster, which has a very real-looking BART logo reads: "Attention BART riders: Racism, Sexism, Islamophobia, Homophobia, Transphobia and Xenophobia are prohibited in the BART systems at all times. Get your s--- together. #BARTbehavior101." And then it asks riders to report incidents to BART police."

Commuters were stunned.

"Racism — Oh my God! Have we come to that now?" Kathy Bertolucci said. And Brian Dorn admitted to being rendered "speechless."

Buzzfeed editor Sarah Karlan tweeted one of the posters, which has taken off around the web. Stephanie Vanegas of Santa Clara also spotted a poster, which she described on Twitter as "very concise and clear messaging."

Matt McGown saw a poster on the Richmond train Friday morning affixed in the bottom-right corner of a Warriors ad featuring Draymond Green. He likes the ad, albeit a little "flip," but in his mind, the Bay Area needs to "embrace diversity and denounce bigotry."

BART rider Warren Johnson agreed. "I think it's good because we all need to come together and that’s a good start right there," he said.

And while the message seems to be popular among some in the San Francisco Bay Area, BART spokesman Taylor Huckaby said the work is not that of the agency's. In fact, BART is working on its own, more toned-down tolerance campaign after a rider was verbally accosted because of her Assyrian heritage last month.

"We don't prohibit free speech," Huckaby said.

In a tweet, BART stressed that "one has the right to hold vile views. However the Bay is NOT fertile ground for bigotry. Look out for one another."

And in a separate reply to a rider, BART tweeted: "We want to create community and foster empathy, not authoritarianism."

Huckaby said he wasn't sure how many posters were put on the trains, and where this exact one was taken. But he said the posters will be taken down when they are spotted.

"We can't have people speaking on behalf of agency using our logo," Huckaby said.

He added: "Though we can appreciate the value of guerilla art, misrepresenting the District sets a dangerous precedent and is not allowed on the system even when art installations are permitted."