Volunteers find no trace of missing girl

Danielle van Dam

SAN DIEGO, California (CNN) -- More than 200 volunteers joined investigators this weekend searching the surrounding area for Danielle van Dam, the 7-year-old girl last seen more than a week ago.

U.S. Marines from nearby Camp Pendleton were among those who responded to an appeal from the missing girl's parents and trudged through about 25 square miles of canyons, coastal hills and ravines about 80 miles east of San Diego.

Volunteers have found no trace of Danielle, said Dawn Davis of the Laura Recovery Center Foundation, the Texas-based group coordinating the 3-day-old civilian search effort.

"The family realizes that law enforcement is doing their job and are limited in manpower," Davis told CNN on Saturday.

The second-grader's parents, Brenda and Damon van Dam, spent most of Sunday in seclusion at their home.

Last week, police used scent dogs, cadaver dogs, helicopters and search-and-rescue teams in their search. No arrests have been made related to Danielle's disappearance.

RESOURCES Daniellemissing.com     To phone in tips "Danielle Missing" Information Hotline: 1-800-251-9927 San Diego Police Department: (619) 531-2000 1-800-THE-LOST 1-800-CRIMETV

According to statements from police and the girl's parents, Brenda van Dam returned to her home at 2 a.m. on February 2 and noticed a blinking light on the burglar alarm and an unlocked door.

Brenda Van Dam said she went to wake her daughter in her second-floor bedroom and discovered she was not there. The parents also said they found an open outside gate.

The parents have taken and passed polygraph tests, and police have searched their home.

Police, meanwhile, continued to monitor an acquaintance of the van Dams who lives two doors down from them and has been a focus of their investigation.

Thirty investigators spent Thursday searching a remote area of the Imperial County desert after learning that motor home owned by the neighbor became stuck in the sand the day Danielle was reported missing.

Authorities say the man has been "extremely cooperative."