The year's first statewide roundup of unregistered sex offenders resulted in only five arrests.
At least 40 sex offenders were targeted as the roundup began Wednesday, with most suspected of living in the Denver area and in El Paso and Pueblo counties.
Authorities say more than 580 sex offenders in Colorado have failed to register as required by law and are subject to arrest.
The crackdown was led by the Colorado Bureau of Investigation and involves the Colorado State Patrol and sheriff's deputies in El Paso and Pueblo counties. Authorities in Denver, Pueblo, Durango and Montrose also participated.