A large section of unstable rock hangs above the Porteau Cove rock slide that buried the Sea-to-Sky Highway. (CBC)

Highway crew members on Thursday blasted rock off the cliff above the site of a massive rock slide blocking the Sea-to-Sky Highway between Vancouver and Whistler, B.C.

The blasting crew arrived at the rock slide early Thursday morning on a boat loaded with equipment. The rockfall above Porteau Cove buried the highway on Tuesday night.

Crew members drilled holes in the rock overhang, plugged in dynamite and gave a two-minute warning before triggering the explosives around 3 p.m. PT.

The blast begins Thursday afternoon after an eight-man crew drilled holes into the cliff and plugged them with explosives to clear 2,000 cubic metres of unstable rock from above the Sea-to-Sky Highway. (CBC)

The crew is trying to bring down a four-metre-thick portion of the cliff, after which engineers will further inspect the rock face for stability and safety, said Mike Oliver, the geotechnical engineer in charge of the project.

"All the dynamite doesn't go off at the same time. There's usually a slight delay and that results in better fragmentation and, I guess, a better blast," he told CBC News before the blast Thursday afternoon.

Oliver said the federal Department of Fisheries and Oceans permitted them to dispose of the rocks just offshore, because it would have a low impact on the environment.

Chunks of rock and debris tumble down the mountain during the blast. (CBC)

Oliver said another blast was scheduled for Friday and the number of blasts that will be required before debris can be removed depends of the rate of the drilling.

The cliff face collapsed between Lions Bay and Furry Creek, burying the two lanes of Highway 99 and a nearby railway line under rock as deep as 10 metres. An estimated 16,000 cubic metres of rock fell onto the highway, the only direct route between Whistler and Vancouver.

A bus carrying one passenger made it through the area just as the slide was coming down. There were no reports of any injuries.

A thick cloud of debris rises as blasted rocks hurtle down the mountainside to land in the ocean. (CBC)

B.C. Transportation Minister Kevin Falcon said before crews can safely move in to clear the rock blocking the two-lane highway, the overhanging rock needs to come down.

"I think there's some technical challenges, where the blasters have to figure out how they can drill in the dynamite into the rock overhang," Falcon said on Thursday morning.

Officials estimated that once the blasting is done it will take at least four more days to clear the massive pile of rock and reopen the highway.

In the meantime, drivers between Vancouver and Whistler have to take a seven- to 10-hour detour through Lytton, Lillooet and Pemberton.

A water-taxi service will move crews to and from the slide site and a helicopter service between Squamish and West Vancouver has been set up to move people with medical needs, emergency workers, and BC Ferries staff needed at Horseshoe Bay.