Two buses collided before one crashed into the front of an Argos store, police have said.
The vehicle mounted the pavement before hitting the front of the branch in Parliament Street, Nottingham, shortly before 16:10 BST.
Four people were taken to hospital but none were thought to have sustained life-threatening injuries, police said.
The road was closed while emergency services dealt with the crash but it has since reopened.
East Midlands Ambulance Service said its crews remained at the scene and it could not provide an exact number of casualties.
At least one passenger was seen being removed from a bus on a stretcher.
Nottingham City Transport said one of those injured was a female bus driver and the company was helping police with their inquiries into the crash.
Commercial and operations director David Astill said: "Our thoughts are with our driver and everyone else involved in this unfortunate episode."
An Argos spokesperson said: "Our Parliament Street store is temporarily closed following an incident.
"We are supporting the police and will reopen as soon as we are able to."