San Diego ? Hundreds of volunteers joined the search Saturday for a missing 7-year-old girl after the arrest of a neighbor and the discovery of bloodstained evidence lent grim urgency to the task of finding her.

The volunteers, carrying bright red tags to mark potential evidence, set out early for the foothills and desert east of San Diego to hunt for any sign of Danielle van Dam, whose gap-toothed smile adorns thousands of missing person fliers.

Brenda van Dam, facing the camera, hugs volunteers at a search center in San Diego and thanks them for helping to search for her 7-year-old daughter, Danielle. The arrest Friday of David Westerfield on suspicion of kidnapping Danielle spurred hundreds of volunteers to show up Saturday at the center to look for clues to Danielle's whereabouts.

Danielle’s parents, Damon and Brenda van Dam, said they were encouraged by the arrest Friday of David Westerfield, a 49-year-old neighbor, on suspicion of kidnapping their daughter.

They urged volunteers to continue helping with the 22-day-old search.

“We’ve got to focus. We’ve got a job to do, and that’s to find Danielle,” Damon van Dam said. “There’s still a little bit of hope that we will get her back.”

Danielle’s parents discovered their daughter missing the morning of Feb. 2. Police said they believed she was abducted from her second-floor bedroom of the family’s north San Diego home sometime after her father put her to bed.

Westerfield, a divorced father of two grown children who lives two doors away from the van Dams, has a 1996 conviction for drunken driving but no violent criminal history, police said.

Investigators began focusing on the self-employed engineer shortly after Danielle disappeared. He was at the same bar for a while that night where Danielle’s mother, Brenda, went with friends while Damon van Dam stayed home with their daughter and two sons.

Westerfield set off in his motor home to the beach and desert the next day.

Authorities said they found traces of Danielle’s blood in the motor home and on an article of Westerfield’s clothing. They also confiscated child pornography from his home, Police Chief David Bejarano said.

Westerfield will be arraigned Tuesday.

“I’m confident that they got the right guy,” said Damon van Dam, 37, an engineer for a San Diego wireless technology firm.

Many volunteers Saturday said their own children’s safety made the search compelling.

“It just hit home,” said Steve Cassarino, a father of two who had been among searchers last week and returned Saturday despite a bad case of poison oak. “It could happen to anybody, any time.”

Another volunteer, Gary Lowe, said he couldn’t bear the thought of the van Dams never knowing what happened to their daughter.

“My main motivation is the fear that she will never be found and they will have to live with that uncertainty for the rest of their lives,” he said.