U.S. Marshals have arrested 13 sex offenders in Iowa, claiming they were some of the most wanted people in the state. Seven of the 13 people arrested had been convicted of crimes against children younger than 13, Marshals said Friday. All 13 had avoided registering as sex offenders in Iowa. The Marshals sent three cases to federal prosecutors in Iowa for possible criminal charges. There are more than 6,500 registered sex offenders in Iowa, and 49 remain on Iowa’s most wanted list. The Marshals did not identify any of the arrested sex offenders. They said the operation, dubbed Operation Most Wa…