At least one person was killed in a multi-vehicle crash on the Coquihalla Highway on Sunday that kept the northbound lanes closed between Hope and Merritt for about 10 hours.

The crash involved six vehicles and a pedestrian. According to witnesses, a semi-truck was one of the vehicles involved.

RCMP said Monday that a pedestrian who stopped to assist after the initial single-vehicle collision was struck and killed. He was a 35-year-old man from the Lower Mainland.

Around 2 p.m., an air ambulance lifted a 78-year-old man with critical injuries from the scene. His injuries have since been downgraded to serious.

Two more people with minor injuries were also transported to hospital in Merritt.

The collision happened around 12:30 p.m. about 32 kilometres south of Merritt near the summit of Larson Hill.

One transport truck operator who frequently travels on Highway 5 expressed his condolences on Facebook.

"The Coquihalla is my work place as a trucker," said Calvin Shupe. "When someone dies in my workplace it definitely hits the heart."

Police are continuing to investigate the crash and say factors could include speed and changes in highway conditions between sunny and shaded areas.

The Central Interior Traffic Services unit in Merritt is asking for witnesses to the crash to come forward by calling 250-378-4262.