A rockslide that dropped boulders the size of semi-trucks has forced the Colorado Department of Transportation (CDOT) to close I-70 in both directions. Officials are unable to provide an estimate on when the road will reopen as damage is extensive on both east and west bound sides.

CDOT spokesperson Stacey Stegman said the boulders were big enough to punch holes into the surface of the highway. Some are large enough that moving them as they are may not be an option – they instead will have to be blown apart into smaller pieces.

CDOT reported on Twitter that the boulders ranged in size from 3 to 10 feet with the largest weighing 66 tons. The largest hole on the westbound side of the highway measures 20 feet by 10 feet and the largest on the eastbound side measures 6 feet by 6 feet.

• Slideshow: Monstrous rockslide forces closure of I-70 in Colorado

The slide occurred near mile marker 125, west of Hanging Lake Tunnel. Officials said they were lucky the slide occurred at 12:09am when traffic on the highway was at a minimum.

Interstate 70 is closed in both directions between mile markers 116 and 133. CDOT says it could be a couple of days before traffic is able to utilize the route.

The shortest detour around the slide area is not a quick one requiring nearly a 200 mile route. Drivers are being encouraged to use U.S. 40 through Steamboat Springs or U.S. 50 through Montrose and Gunnison.

For more on this story including the history of putting I-70 through the canyon, please visit the Denver Weather Examiner.