It could be midnight Thursday before crews can clear a massive mudslide that has blocked the Trans-Canada Highway in both directions in the Fraser Valley east of Vancouver.

At least one driver suffered minor injuries in the slide, which did not hit any homes.

Tonnes of debris roared down over four lanes of the highway and a railway line at about 10:15 a.m. PT Wednesday between Chilliwack and Hope, near the Herrling Island Road exit.

It left a mountain of mud measuring 3,000 square metres and several metres deep in places.

Lynn Orstad of the Fraser Valley Regional District said a car was struck by the debris and rolled over twice, but the female driver escaped with only a bruised knee.

Crews have checked whether any other vehicles were caught in the slide and have seen no sign of other victims so far, but admit the debris field is too deep to be certain.

The debris also swamped a CN Rail line, stopping a freight train, but there was no derailment and no members of the train crew were hurt.

The RCMP said detours are in place to move traffic around the site.

Woman shaken

The woman who escaped from the car was shaking as she walked into a gas station, a cashier who works there said.

The sole occupant of this car, flipped on its roof by the slide, was able to escape with a bruised knee. (CBC)

"She was shaking, literally," Cindy Mackin said from the rural truck stop in Rosedale, B.C.

"I actually talked to a lady who crawled out of it," Mackin said of the slide, more than 100 kilometres east of Vancouver.

"She said she seen the trees coming down and she slammed on her brakes and then she seen it basically happen right in front of her."

Transportation Ministry engineers and geological technicians aboard the RCMP's Air 1 helicopter are conducting a fly-over to assess slope stability and determine whether rescue operations can be resumed, police said.

The RCMP has also established a command post in the area.

Initially the mudslide covered the eastbound side of the highway before spreading to the westbound lanes, according to the RCMP.

That closed to traffic in both directions, and traffic is being diverted to Highway 7 via Highway 9 through Agassiz, according to Drive BC.

Geotechnical engineer Frank W. Baumann, who just finished a report for the regional district on the landslide at Sunshine Valley, east of Hope, that occurred on May 25, said the area affected Wednesday is well-known as a particularly slide-prone zone.

"Some are natural [for very steep and wet ground], and others are caused by old and unstable logging roads that were never properly deactivated," Baumann said in a statement.

With files from The Canadian Press