Fugitive sex offenders or those who failed to register their address per state law are being rounded up this week.

The United States Marshals Service and a violent offender task force in Tucson began arresting offenders Tuesday. The operation will continue through Thursday, Deputy U.S. Marshal Daniel Leyva, said in a news release.

“Additionally, a compliance operation with U.S. Probation, Arizona Department of Corrections – Parole Department, and Pima County Adult Probation will be conducted on Halloween night to ensure convicted sex offenders on supervision are not participating in trick-or-treat activities,” he said.