More police officers joined a search for clues Saturday in what authorities described as a shallow grave in the rugged Utah desert as part of a nearly two-year investigation into the disappearance of a missing mother.

Two previous days of digging have turned up nothing at the site, where the soil inspection process has taken so long that more searchers were enlisted along with a state anthropologist who is an expert in identifying human remains.

Investigators remained confident but acknowledged they still don't know whether the site is related to the disappearance of Susan Powell.

"We're all very hopeful," West Valley City Lt. Bill Merritt said. "I guess it's 50-50 at this point."

The search was halted abruptly Friday when a rainstorm swept through the area.

Cadaver dogs led police to the gravesite on Wednesday just off a dirt road near the base of Topaz Mountain, a popular rock-hounding spot in remote central Utah. The site is more than 130 miles from the location where Powell was last seen at her West Valley City home on Dec. 7, 2009.

Authorities have been searching the area since Monday. On Wednesday, they said they found human remains but later backtracked, clarifying that cadaver dogs had hit on the site but no remains had been found.

The area is about 30 miles south of a spot where Powell's husband, Josh Powell, told police he took his two young children camping on the night his wife vanished. He told police he and their young sons -- then 4 and 2 -- left his wife at home about 12:30 a.m. The 4-year-old confirmed the trip to police.

Josh Powell is the only person of interest in the case, although he has never been arrested or charged. He has denied having anything to do with her disappearance and said he believes his wife ran off with another man.

Susan Powell was 28 when she was reported missing after she failed to show up for her stockbroker job.

Investigators have dug down about two feet at the gravesite but don't intend to go further until the soil is sifted and closely inspected.

So far, no bones or tissue have been discovered. Instead, forensics specialists were finding dozens of small items that could be rocks or bone fragments, Merritt said.

Susan Powell's father, Chuck Cox, was escorted to the scene Friday for a look at the excavation effort.

He believes the area amid central Utah's sagebrush-dotted high desert and jagged mountains is a logical place to conduct the search because Josh Powell had camped at nearby Simpson Springs.

Cox, a former investigator for the Federal Aviation Administration, said he had long-believed the search for his daughter would be a lengthy process.

"There's no real false hope, it's just another step in the investigation," Cox said. "Every day is hard for the family. Life goes on, and so you go on the best you can. It's something you have to live with."