Witnesses said “scared and crying” schoolchildren were among the passengers injured after the double-decker collided with a repairs shop in on Tuesday morning.
At least 19 people were injured and treated at the scene by the London Ambulance Service (LAS), including a trauma team from the capital’s Air Ambulance.
Of these, five people were taken to hospital.
Katriye Osman, who dialled 999 after hearing what sounded like a “really loud explosion”, described the incident as “traumatising”.
Ms Osman, who witnessed the aftermath from outside her beauty salon, said around 50 or 60 children were standing around the vehicle after the collision.
“It was absolutely awful,” she said, adding that she was “really shaken up by it”.
Video and images from the scene show the front of a shop partially destroyed and a large police and ambulance presence.
Fire crews used specialist equipment to free the driver following the crash.
The owner of a local cafe who helped with rescue efforts said a number of schoolchildren were among the injured passengers found "scared and crying" inside the bus.
Eric Garip, 38, told the PA news agency he rushed out of The Corner Cafe after hearing a "big bang" on the opposite side of the road and began trying to carry people out through the emergency door of the bus.
"There were a couple of kids on the floor," he said. We were trying to take the kids out and they were panicking. I spoke to the driver and said to come out, he said: 'I can't, I'm stuck'."
Mr Garip added: "Some parents were in the bus as well, crying. I tried to calm them but it was a big shock. We went upstairs and told the kids to come out but one was on the stairs so [we] were lifting them.
"It was very bad. They were all scared and crying."
An LAS spokesperson earlier said: “We were called at 8.19am to reports of an incident involving a bus on The Broadway, Highams Park.
“We sent a number of resources to the scene including ambulance crews, advanced paramedics, paramedics in fast response cars, incident response officers and members of our Hazardous Area Response Team (HART).
“We also dispatched a trauma team from London’s Air Ambulance.”
Mayor of London Sadiq Khan said: “My thoughts are with everyone affected by this terrible incident.”
London Fire Brigade Chingford station commander Dave Hill said: “Firefighters used specialist cutting equipment to release the driver of the bus.
“Crews made the scene safe and have carried out a systematic search of the building to ensure there are no other casualties trapped.
“There are local road closures in place around the junction of Selwyn Avenue and Winchester Road and we would ask people to avoid the area where possible.”
A spokesperson for the Metropolitan Police said: "At approximately 8.20am on Tuesday 25 January police were called to reports of a bus in collision with a shop in Selwyn Avenue, E4.
"Officers and London Ambulance Service are on scene.
"A number of people have reported suffering injuries and are being treated at the scene.
"Road closures remain in place around the junction of Selwyn Avenue and Winchester Road.
"Inquiries into the circumstances remain ongoing."
Road closures are in place while emergency services work at the scene.
Transport for London said it is investigating the incident.
Louise Cheeseman, TfL’s director of buses, said: “Our thoughts are with everyone involved in the bus collision in Highams Park this morning. We have support available to anyone affected by this incident and a full investigation is underway.”
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies