(CNN) -- Giant rocks came tumbling down a snowy Colorado mountainside early Monday, punching gaping holes in the interstate below, the Colorado Department of Transportation said.

The rock slide at Glenwood Canyon halted travel on Interstate 70 between Glenwood Springs and Dotsero, about 18 miles east, according to the department. Glenwood Springs is about 120 miles west of Denver. It is unclear when construction crews will complete enough work to open at least part of the roadway.

About 20 boulders struck the interstate shortly after midnight, the transportation department said. They ranged from 3 feet to 10 feet in diameter, with the largest weighing an estimated 66 tons, the department said on its Web site.

About eight holes or dips were left on the interstate. Road underwiring was exposed and rock crumbles surrounded the damage, the department said. The largest hole measured 20 feet by 10 feet -- bigger than a full-size SUV.

Rocks were scattered over a 100-yard stretch of the road. A steel guard rail and median barrier were also damaged. The damage resembles a major rock slide in the area back in 2004, the department said.