Police cars block off the roads leading into Tiananmen Square. (STR/AFP/Getty Images)

Tiananmen Square, the vast public space in Beijing's heart, is so politically sensitive that it took mere moments after a car crashed into the square on Monday for the plainclothes police who stalk the square around-the-clock to completely clear the space and erect large cloth barriers to keep out prying eyes. Web censors flew into action, deleting and blocking online discussion of an incident that would have been major news in almost any other country. Even Western photo wires, perhaps unsure of how to read the highly unusual crash, initially tagged their photos "CHINA-UNREST-ACCIDENT-TIANANMEN."

The photos are really something, both for hinting at the severity of the crash and for foregrounding the official clampdown. I've posted all of the photos we have access to thus far. And some more context on the crash is below.

Vehicles travel along Chang'an Avenue as smoke raises in front of a portrait of Mao Zedong (Staff/Reuters)

There is, as yet, no indication that the car crash was anything more than an accident. The jeep careened over security barriers and into the square where it burst into flames, killing two pedestrians and the car's three passengers, and injuring 38 people. But the reaction is a reminder of the extreme sensitivity around Tiananmen, which is most famous in the West for the 1989 protest movement that ended with a bloody military crackdown.

Traffic policemen walk past plainclothes policemen placing green net shields in front of Tiananmen Gate (Andy Wong/AP)

Public gatherings at the square are forbidden and quickly broken up by plainclothes police. This March, a British TV correspondent was reporting from the square when, mere moments after saying the word "1989," he and his crew were whisked into the back of a police van. At moments of political sensitivity, in apparent fear that an activist might attempt to self-immolate at the iconic site, guards will appear around the square dressed in firefighter gear and bearing fire extinguishers. So one can only imagine the official reaction when they heard that a car had crashed into the square and, apparently, exploded.

A Chinese traffic officer keeps watch on vehicles passing at Tiananmen Square outside the Forbidden City. (Rolex Dela Pena/EPA)

Vehicles travel along Chang'an Avenue as smoke rises in front of a portrait of Mao Zedong at Tiananmen Square. (Staff/Reuters)

Plainclothes police hold barriers before the scene of a car crash at Tiananmen Gate. (Ed Jones/AFP/Getty Images)

Here, for context, are photos of the square under normal circumstances. It must have been quite a task to clear it of visitors so quickly.

Visitors walk outside the Forbidden City at Tiananmen Square in Beijing. (Rolex Dela Pena/EPA)

Chinese men wearing masks are seen outside the Forbidden City at Tiananmen Square in Beijing. (Rolex Dela Pena/EPA)