Updated

A search in the Utah desert for a missing mother took a strange turn Thursday when the site that authorities said contained human remains turned up no body parts by the end of the day.

Cadaver dogs discovered the location this week amid a renewed search for Susan Powell, and investigators declared that they had found human remains. But authorities later said that after digging into the site, they had found no remains. Police did not say why they earlier stated they had found human remains when they hadn't seen any.

"Right now, we haven't found anything except for these scents that these dogs are picking up," said West Valley City Police Lt. Bill Merritt. "We have not come across bones."

Because the site in a remote area of central Utah is on government land, a Bureau of Land Management anthropologist was brought in to determine if it was part of an ancient burial ground. The scientist later said it wasn't, but instead showed signs of recent disturbance.

Investigators then began sifting through what was described as a shallow grave.

"We're not looking at some ancient burial ground," Merritt said. "This is not going to be some cowboy from the West."

Merritt said later Thursday that authorities had only begun to dig into the dirt in the afternoon. By the end of the day, they had dug several feet down, but came across no remains.

"Shovel by shovel full," Merritt said. "Every shovel full that comes out is being sifted through. It's a painstaking process.

"We would love this to be a break," he added. "We hope, to a certain extent, that it is not Susan because that would mean that she is maybe alive somewhere."

West Valley City Police Chief Thayne "Buzz" Nielsen said the area where the dogs indicated remains would be found was beneath what appeared to be a shallow grave covered with dirt.

"They have found what looks like a grave where the dirt has been shoveled and moved around a little bit," Nielsen said.

Police have been searching since Monday in the area near Topaz Mountain in Juab County for any clues in the disappearance of Susan Powell. The site is about 135 miles southwest of the location where she was last seen at her home in West Valley City on Dec. 7, 2009. It is also just about 30 miles south of where Powell's husband, Josh Powell, told police he took his two young children camping on the night his wife vanished.

He is the only person of interest in the case, but has never been arrested or charged.

Merritt said the discovery "fits in with what we've been looking for."

Asked whether he was hopeful Susan Powell's remains would be found there, Merritt called it "50-50 at this point."

Authorities planned to resume excavation of the site Friday morning, and Susan Powell's father, Chuck Cox, planned to be there.

Susan Powell was 28 when she was reported missing Dec. 7, 2009, after she failed to show up for her stockbroker job. The case has cast a harsh spotlight on Powell's husband, who hasn't returned repeated calls from The Associated Press. In a string of national television interviews last month, however, he denied having anything to do with her disappearance.

The area where authorities are now working is in a rugged remote section of Utah's central high desert surrounded by grasses and sagebrush and punctuated by jagged mountains rising from the flat landscape. At the time of year Susan Powell vanished, it would have been bitter cold, the ground frozen, possibly even snow-covered.

Josh Powell was driving a minivan that night. He has told police he left his wife at home about 12:30 a.m. on that Dec. 7 to go winter camping in freezing temperatures with their young sons -- then 4 and 2 -- just about 30 miles from where police are now searching. The 4-year-old confirmed the trip to police.

Josh Powell has said he believes his wife ran off with another man.

Merritt said the site would have been difficult to reach in December but not impossible.

"Impossible? I can't say that," he said. "Difficult? It probably would be."

There have several instances in the past two years where speculation swirled that a body discovery might have been Susan Powell.

The latest came in May when remains were found in the desert about 50 miles southwest of Salt Lake City. Authorities later said it was a young adult male.

Last month, investigators searched mine shaft-dotted mountains near Ely, Nev., and later served a search warrant at the Puyallup, Wash., home that Josh Powell shares with his father, seizing computers and journals.

This latest search is in an area popular for gem and rock hunters. Police have said Josh Powell liked to rock hunt in the area.

"From the very beginning he clearly indicated he had been in and around the area," said West Valley City Police Sgt. Mike Powell, who is not related to the family of the missing woman.

Susan Powell's father, Chuck Cox, expressed doubt that the remains belonged to his daughter because of how difficult it would have been to access the area in winter.

"We're just waiting," he said.

The Powell family put out a statement late Wednesday urging police to put out details about the remains.

"With very little information available to the public, we can only hope that additional information is released quickly to minimize heartache to those of us who love Susan," it said. "In the meantime, we continue to hope for Susan's safe return."

Last month, the case turned salacious as family members on both sides sparred over accusations of sex and lies.

Josh Powell's family claims Susan Powell was sexually promiscuous, emotionally unstable and suicidal, accusations her family denies.

In yet another strange twist, Steve Powell, Josh's father, claimed he and Susan Powell were falling in love and even implied a sexual relationship had occurred.

Susan's family said the allegations are false, and that it was Steve Powell who initiated unwanted sexual advances.

The feuding between the two sides got so heated that a court commissioner in Washington state last month ordered Chuck Cox and Josh Powell to keep 500 feet apart.