Federal, state and local authorities made 33 arrests during a three-day sweep targeting sex offenders who haven't registered.

U.S. Marshal Kelvin Washington for the South Carolina district said agents from his office, the State Law Enforcement Division and multiple local agencies served 72 warrants between Tuesday and Thursday.

Washington said 28 of the 33 suspects arrested as part of "Operation AWOL" were sex offenders.

"This operation should serve as a message to every unregistered sex offender out there," he said. "You know that you're required to register, and if you don't register, we're going to find you and put you in jail."

Authorities also arrested two suspects on charges of attempted murder, two suspects on charges of armed robbery and one suspect charged with drug-related offenses.

Washington said U.S. Marshals have become active in the arrest of unregistered sex offenders since the service was tasked with the enforcement of the Adam Walsh Act in 2007 that created stricter regulations.

"We've become very heavily involved in the apprehension of ... sex offenders, especially those who cross state lines and fail to register in their new jurisdictions," Washington said.

Washington said the three-day operation also led them to offenders in Florida, New Mexico, North Carolina and Tennessee. They located 20 offenders who have registered in their respective states and were not charged, he said.

The Charleston County, Berkeley County and Dorchester County sheriff's offices, and the North Charleston and Charleston police departments participated in the sweep.

Washington credited the success of the operation to the cooperation of all of the agencies. He said they intend to have similar sweeps across the state.

Reach Andy Paras at 937-5589, aparas@postandcourier.com or on twitter at twitter.com/andyparas.