The rockfall was reported about 7:45 a.m. on Bondad Hill, five miles north of the Colorado-New Mexico line.

One slab came down and separated into two sections when it hit the road.

One boulder was in the shape of a block and measured 8 feet on all sides. The other was 20 feet long, 15 feet wide and 12 feet high, said Nancy Shanks, spokeswoman with the Colorado Department of Transportation.

The rocks covered 1½ lanes of traffic in the northbound direction. No one was injured in the slide.

Road crews spent much of the day blasting the fallen rock in preparation for removal. Traffic was stopped briefly for blasting, but otherwise, both directions of travel moved past the boulders in an alternating fashion on the open lane.

All lanes of traffic reopened shortly after 5 p.m.

Shanks said workers attempted to use a trackhoe to remove unstable rocks, but no safe work area could be found. She said the workers instead dug a large ditch downhill from the slide area to prevent further slides or loose debris from reaching the highway.

Shanks blamed the fall partly on the wet winter and a freeze-and-thaw cycle.

"We haven't seen rocks of this size come down in seven to eight years," she said. "When they come down, they tend to be big."

A rock of similar size fell in the same location on July 28, 1998, nearly hitting a northbound Toyota Tercel. Another rock of nearly equal dimensions fell on the stretch on July 23, 1992.

Minor cleanup was expected to resume today, causing some delays.

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