VANCOUVER -- A serious crash involving 15 to 20 vehicles shut down the Coquihalla Highway southbound between Merritt and Hope for several hours on Thursday.

The crash happened around 4 p.m. in an area known as the Zopkios Brake Check and was described as a "chain reaction pile up," according to BC Emergency Health Services.

Three ground ambulance crews were dispatched to the scene and transported four patients to hospital in stable condition, according to the health agency.

DriveBC tweeted just after 7 p.m. that the southbound lanes of the highway had fully reopened, but drivers were warned to expect delays.