Interstate 70 near Georgetown, CO, was closed in both directions April 8 after a series of massive boulders crashed onto the highway shortly after midnight that morning, The Rocky Mountain News reported.

Although no vehicles were trapped, the newspaper said two tractor-trailers were damaged. One swerved to avoid the rocks, but crashed into a median barrier as boulders stripped the tires off its trailer and tore open its fuel tanks. The other truck was only slightly damaged.

A rockfall prevention system was installed on the mountain at the location of the rockslide in fall of 2000, according to the Colorado Department of Transportation. It included a steel fence and cable nets designed to catch rocks before they reached the highway.

However, The News said the system was designed to catch rocks the size of a microwave or smaller. Many of the boulders involved in Thursday’s rockslide were larger than refrigerators.

The highway was closed about 8 hours.