According to RCMP, at around 7:35 a.m. PT Saturday morning, a southbound vehicle carrying two passengers lost control and collided head-on with a truck about 5 km north of Lions Bay.
The accident occurred on an undivided stretch of highway with one lane running in each direction.
Both people in the southbound vehicle were killed, and the two occupants in the truck were taken to hospital.
Squamish RCMP from Sea to Sky detachment are investigating, and have closed Highway 99 in both directions indefinitely.
No details about the victims are available at this time.