Avalanche danger, heavy snowfall and spun-out vehicles prompted transportation officials to close Interstate 90 over Snoqualmie Pass for hours on Monday as a winter storm slammed the Washington Cascades.

The closure extended about 70 miles from North Bend to Ellensburg. Both westbound and eastbound lanes reopened by 8 p.m. Monday.

"We cannot re-open Snoqualmie pass until it is safe to do so," WSDOT Tweeted earlier in the day.

The slide occurred near milepost 51 on the west side of the summit at the Franklin Falls areas and blocked the westbound lanes of I-90, WSDOT said.

"Our avalanche team is assessing the risk for more avalanches to occur, and it is likely that they will need to do avalanche control work in several locations before we can open the highway," said Todd Trepanier, WSDOT's south central region maintenance engineer, in a news release on Monday afternoon.

The release also noted that snow was falling on the pass at a rate of about 2-3 inches per hour Monday afternoon, and "travel over any Cascade mountain pass will be very challenging," during the next 36 hours, when heavy snow is forecast.

No cars were hit by the snow, WSDOT said. The snow was 10 feet deep and blocked all three westbound lanes.

Other cars crashed into each other after they tried to stop in front of the slide, and had to be cleared out along with the snow, WSDOT said.

WSDOT said it would upload photos of the avalanche to its Flickr page as soon as it was able to. We will post some of those photos here when they become available.

The avalanche was previously reported as a "natural slide" by WSDOT. WSDOT said a natural slide was one that wasn't caused by WSDOT.

Pass Cams: Denny Creek | Franklin Falls | Hyak West | Price Creek | Easton