Highway 97 near Summerland B.C. will remain closed until at least Monday morning after the discovery of an unstable and dangerous rock face.

The fault was found shortly before 7 p.m. last night by workers along a part of the route that's been in the midst of a $54-million widening project by Arthon Construction Co. since the spring.

Geotechnical engineers say the fissure is several feet wide and is around 30 feet deep. Rough estimates are that around 300,000 cubic metres of rock are moving on the face.

The shutdown severs the main artery between Penticton to Kelowna in B.C.'s Okanagan region.

Arthon Construction's spokeswoman Jacqui Lloyd says the cliff face is considered dangerous and the unstable face presents a "significant safety concern" for passing vehicles. The company estimates it will take at least a few days to repair the face.

The area is now being evaluated by B.C.'s Ministry of Transportation Geotechnical Engineers for stability and safety.

Northbound motorists are advised to detour via Highway 33 or Highway 3.

The alternate route will add at least a few hours to the trip.