RELATED: Live traffic maps show backup from SF bus crash
Three southbound lanes were blocked during the latter half of the evening commute and traffic backed up through the skyway and back into the city well past midnight.
Ambulances raced to the scene shortly after 8 p.m. where a bus operated by Charter Brothers, overturned on the highway. CHP officials say the bus hit the center median wall and ricocheted crashing on the right side of Southbound 101 with 29 passengers on board.
The CHP says there are 4 to 6 people with major injuries.
The San Francisco Fire Department called a red alert to get hospitals ready and to bring in ambulances.
"Currently the San Francisco fire department has responded with eight ground ambulances, a total of seven engines and our rescue squads," said Jonathan Baxter of San Francisco Fire. "We have probably over 60 firefighters and paramedics on the scene to assess the damage."
He went on to say that first responders cut a hole through the brick wall that separates Highway 101 from Vermont Street to move walking wounded patients to busses where they could be treated.
Eight patients were taken to San Francisco General Hospital -- five women, three men all in their 20s and 30s. Twenty-two patients are in fair condition and one is in serious condition. The driver was not impared.
Engineers arrived on scene to assess damage to the bus, and try to determine what caused the crash.
Officials say they do not know about patients that may have gone to other hospitals.
There is no estimated time of reopening.
Officials say if you do not need to be on Highway 101, or anywhere near the on or off-ramps please stay away. They had issues getting their emergency vehicles to the scene and there is a lot of work left to do.
Stay with ABC7 News for the latest details on this developing story.