The crash happened late Friday afternoon on Highway 97 south of Kersley, B.C. — about 30 kilometres outside of Quesnel, RCMP said in a release.
Four vehicles travelling north were involved — the bus, a car, a pickup truck and a tractor pulling a piece of farm equipment.
There was no immediate information on which vehicles the people killed and injured were travelling in. BC Emergency Health Services said one person was airlifted from the scene while seven others were taken to hospital by ground ambulance.
7 others in hospital
Service spokeswoman Cara Christopherson said of the seven people driven to hospital, five are in stable condition and two are in critical condition.
Greyhound Canada spokeswoman Allison Morrison said the bus was travelling from Clinton to Prince George.
There were seven passengers and the driver on the bus, and all taken to a local hopsital with unknown injuries, she said.
"Safety is the cornerstone of our business,'' Morrison said. "We are fully co-operating with the local authorities as well as conducting an investigation of our own.''
RCMP said the cause of the crash has not been determined, but it's believed that alcohol was not a factor.
Police said a collision reconstructionist from Williams Lake had been called to assist with the investigation.
Highway 97 was closed in both directions for several hours near Kersely as police investigated.