Around 3:30 p.m. Tuesday afternoon, a driver reportedly blew a stop sign at the corner of Hayes and Steiner on the East side of Alamo Square, smashed into another vehicle and sent both vehicles spinning back into Hayes Street. The wreck is currently blocking Muni service on the 21-Hayes route.

According to SFist's own Jay Barmann, who was in the area at the time of the crash, one of the two cars was trying to make a turn. Other witnesses claimed one of the drivers may have been speeding away from an earlier accident on Divisadero:

There were three people in the black car, which had been turning right onto Hayes from Steiner, and was hit by a woman driving a white car, who, reportedly had hit two other cars on Divisadero, and coming down the Hayes hill by the park, ran the stop sign at about 65-70mph. This is a bystander’s estimate.

Everyone was breathing when they got them out of the car.

Both cars appeared to be heavily damaged. Ambulance and fire crews were on the scene and Haighteration reports all four people injured were taken to a trauma center with life-threatening injuries.

Muni buses were being re-routed in both directions: We will, of course, up date when if/when we know more.

Update: We had conflicting reports coming in from people who claim to have witnessed the incident. We've made some edits to reflect the latest info.

In other news, a Google bus was temporarily inconvenienced by SFPD's collision investigation.