The tow truck was stopped at the side of the Coquihalla Highway, about 30 kilometres south of Merritt, assisting another vehicle.
The Interior Health Authority says all but two of 25 patients in its care have been discharged.
It did not have a condition on the two remaining patients, but the BC Ambulance Service said Saturday that two people suffered life-threatening injuries in the crash.
Hospitals in the Fraser Health Authority received an additional 13 patients following the crash, but couldn't immediately provide numbers on how many were still in hospital. None of the patients it accepted were seriously injured.
Meanwhile, the B.C. Ministry of Transportation announced Sunday it would conduct an audit of the company's overall safety record including its drivers and the mechanical operation of its buses
"I understand that the road was bare and dry and the incident happened on a straight section of highway," the minister said in a statement.
Charges are pending against the driver of the Universal Coach Lines tour bus that slammed into the tow truck.
RCMP Sgt. Mike Pears said the tow truck had been called to assist a car that was disabled after it hit a deer.
He said both vehicles were pulled over to the side of the road, but the tour bus failed to slow down or move over.
Pictures from the scene showed the front of the bus sheared off and a tow truck and red hatchback with extensive damage.
Last August a B.C. tour bus crashed about 50 km away on the same highway, injuring 43 people, five of them critically.