The two passengers who were stuck on the top deck of the bus that crashed into a tree in Kennington have now been safely removed.
A reporter at the scene said both had been rushed to hospital with serious injuries to their legs.
"Firefighters using cutting gear have now freed the final two casualties from the top deck of the crashed bus in Kennington," London Fire Brigade said.
Reporting from the scene, Press Association reporter James Edgar described the two passengers being removed from the bus.
"One person just been removed from back of bus on stretcher covered in white blankets. Don't think it's the 19-year-old."
One person just been removed from back of bus on stretcher covered in white blankets. Don't think it's the 19yo
— James Edgar (@JamesEdgarPA) December 20, 2013
He said London Ambulance Service told him two people, one man one female, had serious leg injuries and that they have been taken to hospital by air ambulance.
Currently, two people are in a critical condition. It is thought one of those seriously injured is a 19-year-old woman.
In total, 23 people were described as "walking wounded", while seven people are still being assessed.
The Met Police issued a statement denying that the bus had swerved to avoid an oncoming emergency vehicle: "There was no police vehicle involved in the collision. Two uniformed police officers were travelling on the bus, both were injured, we await further details."