Three children and two adults have been taken to hospital after a double-decker bus hit a shop in north-east London.
The crash happened on Selwyn Avenue in Highams Park, Chingford, at about 08:20 GMT, the Metropolitan Police said.
London Ambulance Service (LAS) said 14 other people were treated at the scene, near Highams Park Overground station, but did not need hospital treatment.
An eyewitness told the BBC that the driver said "his brakes had failed" and he had to be cut free by firefighters.
Ben Taylor-Coleman, who had just dropped off his daughter at nursery, described children on a zebra crossing "jumping out of the way" of the bus.
'Blood and petrol'
"The bus carried across the kerb and into the shop on the other side," he told the BBC.
"I called 999 and as I was speaking to police I was helping people getting off the bus - as were lots of others.
"Some had hurt themselves and the driver told me he was trapped in his cab.
"There was plenty of crowding and a few local shopkeepers came out with water and toilet roll to mop up blood and petrol.
"Paramedics arrived in less than 10 minutes and the fire service cut the driver out of his cab."
The owner of a local café 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, described 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."
Mayor of London Sadiq Khan said his thoughts were with those affected by the "terrible incident".
'Full investigation under way'
The Met Police said it was investigating the crash and officers were carrying out inquiries.
Data published by TfL showed that last year 10 people died as a result of incidents involving buses, with 17 others seriously injured.
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 under way."