A magnitude 4.1 earthquake shook Steamboat Springs near midnight Friday.
According to the U.S. Geological Survey Web site, http://earthquake.usgs.gov, an earthquake originating 15 miles northeast of Steamboat and 3.1 miles underground was registered at 11:57 p.m. Friday.
Dan Blakeman, a geophysicist with the Denver-based USGS National Earthquake Information Center, said seismographs detected the earthquake.
"We definitely had an earthquake," Blakeman said. "I'm certain quite a few people felt it."
It wasn't immediately known how far the earthquake's tremors reached in the region, though they were reported from the east side of town to the west side in Steamboat II.
Local dispatchers reported receiving more than 300 phone calls from area residents late Friday and early Saturday.
Moffat County dispatchers didn't report any earthquake-related phone calls.
It wasn't immediately known whether the earthquake caused damage or injuries.
A magnitude 4.1 earthquake is considered light by USGS standards, and damage is minimal to none.
"It can give you a pretty big shake, but it generally doesn't cause much damage," Blakeman said. "But you never know what might happen. It might knock stuff off of shelves."
Colorado is considered a light earthquake activity zone.
-- Brent Boyer contributed to this report.