BAKERSFIELD, Calif. - On Halloween, thousands of kids walked around neighborhoods trick-or-treating.

State parole officers were also milling around town, checking in on those who are not supposed to participating in the holiday.

It is called  "Operation Boo."

It's a statewide effort to make sure the doors kids knocked on were safe.

"Tonight is when we go to make sure the parolees are not participating in Halloween," said James Stanton, the unit supervisor for the California Department of Corrections and Rehabilitation.

In its 19th year, Operation Boo splits officers into seven teams. They are spread across the Bakersfield area to make sure sex offenders are staying away from trick-or-treaters.

"We're trying to protect the children out there," said Stanton. "(We) make sure families have a good, safe Halloween. We aren't letting the sex offenders, participate in Halloween, so just trying to keep them away from the kids."

Parolees have a 5 p.m. to 5 a.m. curfew, are not allowed to have any outside lights on at their homes, have decorations or candy out, and can only open the door for law enforcement.

"We don't want kids going up and knocking on one of those doors and a parolee answering it," said Stanton.

A total of seven teams checked on nearly 80 parolees in and around the city of Bakersfield.

Officers arrested six people for violating parole.