Teams are making good progress searching a remote area of the Utah desert for signs of a mother missing since 2009, and the effort will likely continue for several days, police said Wednesday.
"There are a number of areas that remain on our map that we still need to cover," said West Valley City police Sgt. Mike Powell. "We're gonna be here for a couple of more days."
Searchers have been working on foot, all-terrain vehicles and horseback for more than a week in the search for Susan Powell, who is not related to the sergeant. Cadaver dogs trained in detecting a decomposing human body and a state police helicopter have also been employed.
So far, police estimate they have covered more than 50 square miles with the help of search-and-rescue crews from six county sheriff's offices.
Police are working near Topaz Mountain, a popular rock-hounding area about 135 miles southwest of West Valley City, where the mother of two was last seen in December 2009. Wednesday's efforts were expected to take searchers about 30 miles north and east of where they have been focused over the past week, Powell said.
Investigators haven't said specifically what they are looking for but have recovered numerous items that "don't belong in the natural environment," including blankets and clothing, which are being documented and removed for a closer look, Powell said. Last week, cadaver dogs led investigators to what appeared to be a shallow grave, but after two days of excavation, police said they had found only a collection of charred wood chips. About 100 pieces of wood have been removed from the site for examination and possible testing by a forensic anthropologist.
Lt. Bill Merritt, who supervises West Valley City's major crimes unit, has said it's possible the dig site may have been a crime scene at some point. Merritt said last week that he didn't know whether DNA evidence — should it exist — could be recovered from burned wood.
In an email Wednesday, Salt Lake City forensic DNA testing expert Tim Kupferschmid said it is difficult, but possible, to extract a DNA profile from burned wood, although fire will degrade and eventually destroy DNA evidence.
"The quality of the DNA depends on the length of time in the fire, the heat of the fire and the amount of starting biological material present," Kupferschmid, the executive laboratory director for Sorenson Forensics, told The Associated Press.
Susan Powell's husband, Josh Powell, has been named the only person of interest in the case. He has not been arrested or charged.
Police are searching near Topaz Mountain in part because it's about 30 miles south of Simpson Spring, a Pony Express Trail campground where Josh Powell told police he took the couple's young children — then aged 2 and 4 — on a winter camping trip in the hours before his wife disappeared. The Powells' 4-year-old son has confirmed the trip to police.
Last month, West Valley City investigators also searched the mine-dotted mountains outside of Ely, Nev., for clues in the case. Investigators have said both searches were triggered by information gathered from search warrants. Just after Susan Powell's disappearance, warrants were served on Josh Powell's West Valley City home and the family minivan, which he said he took camping.
More recently, police served a warrant on the Puyallup, Wash., home where Josh Powell and the children now live with family. Josh Powell's father, Steven Powell, has said investigators removed computers and journals belonging to Susan Powell from the home.
Susan's father, Chuck Cox, spoke about the search during a live interview with a Seattle radio station Wednesday. The retired Federal Aviation Administration investigator said his faith and his understanding of the investigative process help him deal with the unanswered questions about his daughter's disappearance.
"I know they are doing a very detailed, methodical investigation and that they are going to uncover the facts," Cox told KIRO-FM. "I know that's our best chance of finding her and getting her home."