B.C.'s Transportation Minister Kevin Falcon says it's incredible no one was hurt during a massive rock slide 50 kilometres north of Vancouver.

At least 16,000 cubic metres of debris came crashing down on the road near Porteau Cove just before midnight Tuesday, burying both lanes of traffic in truck-sized boulders and covering a parallel railway system in both directions.

It was a close call for a shuttle bus driving through the area at the time of the slide. The passenger and driver escaped injury, even though the bus was showered with boulders, smashing most of the windows.

Transportation officials toured the area by helicopter Wednesday afternoon. They say major stabilization, bolting and blasting must be completed before the roadway is reopened.

Highway 99 is closed from the Furry Creek Bridge to Horseshoe Bay.

Geotechnical engineers spent most of Wednesday assessing the stability of the area.

Falcon suggests the highway could be closed for up to five days.

Rail lines are also affected. Rock piles have spilled onto CN Rail tracks that run parallel to the highway, preventing its two freights from completing their daily trip from Prince George to North Vancouver.

A spokesperson for CN Rail says they are looking into rerouting freight traffic through Kamloops and Boston Bar.

The Sea to Sky Highway is currently undergoing a $775 million upgrade for the 2010 Olympic Games.

The route is being improved to ensure it can handle all the traffic expected between Vancouver and Whistler during the 2010 Olympics, but critics fear the work is not enough to guarantee the highway will remain open during the entirety of the event.

B.C.'s premier, Gordon Campbell, says officials are dealing with the slide as quickly as possible but it's not in a construction zone.

"This is an area that was not touched by the improvements that we're making," Campbell said. "But we will be doing an inventory of the entire road to make sure that it is safe.

Officials from the Transportation Ministry say the slide comes as a surprise to geotechnical officials. The area had experienced previous slides but it was not identified as an area prone to something major.

This weekend, traffic jams clogged the Sea to Sky from Horseshoe Bay to Pemberton, as more than 40,000 music fans attended the inaugural Pemberton Festival.

The indefinite closure of the winding and picturesque road leaves just one way out of the upper Howe Sound, Whistler and Pemberton areas.

Drivers have been advised to find alternate routes.

"The only route out would be through the Duffy Lake, and around, down through the lower Interior which would take seven to eight hours to get to Vancouver," said Ritchie.

Local helicopter companies are offering charter flights between Vancouver and Whistler or Squamish for travellers who can't wait for the Sea to Sky to re-open.

Tuesday's slide is only the latest incident that raises questions about safety on this key transportation artery. More than 14 major slides on the Sea to Sky have claimed at least 12 lives in the past century.

A 1991 slide near Lion's Bay, B.C., closed the highway for 12 days.

Smaller slides are common, causing major headaches for commuters and area residents. The road's windy curves and two-lane sections are blamed for many of the more than 800 accidents in the last five years alone.

The winding mountain highway was seen by some as the Achilles heel during the 2010 Olympic bid, drawing protests from local residents, who are opposed to highway expansion.

The International Olympic Committee said the road to Whistler was their prime concern for Vancouver's 2010 bid until B.C.'s provincial government committed $600 million for road improvements.