Three people died on the spot while 17 others were seriously injured along the Bulawayo-Harare highway, 40 kilometres outside Kwekwe from Gweru.
The Nissan Caravan commuter omnibus they were travelling in swerved to the right lane, overturned and rolled several times before plunging into a stream.
Eyewitnesses said the driver failed to negotiate a curve and lost control of the vehicle and it rolled several times throwing passengers outside before landing on its side in a nearby stream.
Gweru Fire Brigade sub officer Mr Ephraim Manzera said the vehicle hit a bridge and it burst its front tyre before rolling several times.
Midlands police spokesperson Assistant Inspector Ethel Mukwende confirmed that three people died on the spot and that as police they had no full details of the accident as they were still assessing the accident scene.
The injured were taken to Gweru Hospital and the names of the deceased are still being withheld until their next of kin have been advised.