(Hillsboro, OR) -- The Washington County Sheriff's Office says it spent more than a month checking on 510 sex offenders to make sure they're in compliance with registration requirements. Tweleve of the people weren't living at their reported residence, 28 sex offenders were investigated for being out of compliance and 19 people were arrested or cited for Failure to Report as a Sex Offender. The U.S. Marshals Service and Oregon State Police provided help for the operation.