The crash happened on Highway 10 between Highway 91 and 120th Street the scene at around 3:15 p.m. PT Monday afternoon.
Sgt. Sarah Swallow told the CBC preliminary investigations suggest a westbound vehicle lost control and crossed into oncoming traffic.
"Obviously the circumstances that caused that will be under investigation," said Swallow.
"I believe it was probably heavy rain in the area... That will be a factor that the investigators will look in to, whether it's rain, visibility, speed."
Delta police tweeted on Monday afternoon, saying they are still in the process of notifying the victims' families.
Highway 10 is now closed in both direction and police are urging drivers to find alternative routes.
Google Map: Highway 10 between Highway 91 and 120th Street
More to come