LOS ANGELES (CBS) —  Three people on probation for sex crimes, including a man with a passageway leading from his bedroom to the basement, were arrested in a Halloween sweep intended to keep children safe, county officials announced Tuesday.

Forty probation officers visited 251 homes in the four-day “Operation Safe Halloween.” and found 229 probationers at home.

People convicted of sex crimes are prohibited from decorating their homes for trick-or-treaters and told to keep their porch lights off and curtains closed so that children get a clear message to stay away. Seventeen of the probationers were in violation of the conditions of their probation.

In one home, probation officers found a door in the floor of the probationer’s bedroom, covered by carpet and a piece of furniture, said Walter Mann, director of the Probation Department’s special enforcement operations unit.

When the officers pulled the door open, they found a 6- to 7-foot drop to a basement with a chair and a rope.

At another home decorated for Halloween, a man and woman, both probationers, came to the door to give out candy when the officers rang the bell. A search of the man turned up methamphetamine.

Supervisor Michael Antonovich thanked probation officers for their efforts today, recognizing their “proactive efforts to keep our community and our children safe.”