SAN DIEGO -- After 18 days with no sign of 7-year-old Danielle van Dam, lab technicians returned to the home of the missing girl with fingerprint materials, according to 10News.

MISSING Danielle van Dam 4 feet tall, 58 pounds Blue eyes, dirty blond hair Possibly wearing blue pajamas Watch Danielle Video Montage INFORMATION (619) 531-2000 Danielle Missing Flyer DISCUSSION Share your feelings, thoughts for van Dam family

A strong chemical that locates fingerprints was placed in and around the van Dam home last week. The lab technicians said the chemical needed to cure for about a week.

Police and volunteers continue to search areas around San Diego County for Danielle. Teams of ten headed to Interstate 8 near Japatul Road Tuesday to look for any signs of the missing girl, 10News reported.

Video

Now Is A Time For Patience

Over the weekend, the van Dam family organized an independent volunteer search of Borrego Springs, Glamis and Ocotillo Wells.

"We need more people. We need to keep it going ... possibly into next weekend," Danielle's father Damon van Dam told reporters Monday.

In the meantime, the van Dams said that they are trying to keep busy.

"You stop and you are alone and all these things come into your head and you have a big breakdown -- like I did last night -- so keeping busy helps you stay sane," Danielle's mother Brenda van Dam said.

The van Dams plan on taking their two sons to counseling later Tuesday.

Danielle hasn't been seen since her father put her to bed on Feb. 1. Her parents said they discovered her missing the next morning.

A neighbor of the van Dams, David Westerfield (pictured, left), has come under close scrutiny, but authorities refuse to call him anything more than a "potential suspect."

Investigators have searched his home and impounded his sport utility vehicle and motor home, and he has provided a DNA sample for analysis, but he has not been arrested.

Last Wednesday, detectives conducted a third search of Westerfield's house -- two doors down from the van Dam home -- and carted away more boxes and bags of what they called "potential evidence."

But police have refused to disclose what they may have been looking for or what they found in the home of the 50-year-old design engineer, who has also been under 24-hour surveillance.

In one of his few public statements, Westerfield told reporters that he spent the weekend that Danielle went missing in the desert in his motor home. That prompted a search of the remote Imperial Valley area where Westerfield said he visited.

Authorities have acknowledged that the odds of finding the girl alive are waning.

"We are not real hopeful on her condition," San Diego police homicide Lt. Jim Duncan told reporters several days ago.