The rockslide was reported around 12:25 p.m. PT Monday approximately eight kilometres west of Standing Rock, between Keremeos and Hedley, B.C.
Witnesses say rocks of all shapes and sizes — including boulders the size of trucks — crashed onto Highway 3, leaving a 150-metre wide debris field.
Three vehicles were involved in the incident, and one female with non-life threatening injuries has been sent to hospital.
The rockslide knocked out transmission lines, causing more than 1,000 homes to lose power. However, a spokesperson with FortisBC says power was restored to all but 280 homes by 3 p.m.
Work crews with the Ministry of Highway and Infrastructure are assessing the damage and say the highway could be closed until tomorrow.
The slide initially knocked more than 100
Drivers are being asked to find alternate routes.
Map: Highway 3 closed in both directions near Keremeos and Hedley, B.C.