Glenwood Springs, Colo. » Crews have begun breaking apart massive boulders that tumbled onto Interstate 70 in western Colorado and forced a 17-mile section of the highway to close.

Colorado Department of Transportation spokeswoman Stacey Stegman says workers are drilling holes in the boulders to insert explosives and blast them into smaller pieces.

The rock slide hit at about midnight Sunday and punched gaping holes in a bridge in Glenwood Canyon about 110 miles west of Denver. No injuries were reported.

All lanes were closed from Glenwood Springs east to the town of Dotsero, and it's unclear when they will reopen.

Up to 25,000 vehicles a day travel that section of highway.

Because of the rugged terrain, the shortest detour adds about 200 miles around the mountainous Flat Tops Wilderness Area.

The largest hole in the roadway was 10 feet by 20 feet. About 20 boulders ranging from three to 10 feet long were scattered on the highway, with the largest weighing 66 tons, officials said.

A 1995 rock slide on I-70 in Glenwood Canyon killed three people.

A slide on Thanksgiving Day in 2004 closed the highway and required nearly $700,000 worth of repairs. No one was hurt because the highway had previously been closed for an unrelated crash.

The Union Pacific Railroad said its tracks through the canyon weren't affected. The tracks carry freight trains and Amtrak's California Zephyr.

Monday editions of the Glenwood Springs Post Independent and the Aspen Times were delivered late because the slide struck between their towns and their printing plant in the town of Gypsum.