"The leads have become fewer and farther between," said Wayne Pyle, the city manager for West Valley City, Utah.
"If nothing comes from it, we do feel like we are close to the end of the investigation," he said.
Investigators found no signs of Powell, missing since 2009, after using dogs to search a rural site near this town in Western Oregon.
"It's been a meticulously investigated case. We've looked at every tip and aspect" and will continue to do so, said Sgt. Mike Powell, a spokesman for West Valley City police who is not related to the missing woman.
In an interview Wednesday night, Susan Powell's father said he hoped the investigators would turn up some sign of her.
"I'm disappointed," said Chuck Cox, who accompanied some of the search dogs on the hunt. "I just don't know where she is, but we'll keep looking for her."
He said the Oregon property had ties to the family.
Susan Powell was reported missing in December 2009 after she didn't show up for work. Her husband, Josh, maintained his innocence and said he took the couple's young boys on a midnight camping trip in freezing temperatures the night his wife disappeared.
In February 2012, Josh Powell locked a social worker out of his home at the start of a supervised visit, then killed himself and the couple's two young children, attacking his sons with a hatchet and then setting the house ablaze. Days earlier, a court had ordered Powell to undergo an intensive psychosexual evaluation as part of a custody dispute.
Josh Powell was never charged in his wife's disappearance, but unsealed documents say authorities found Susan Powell's blood on a floor next to a sofa that appeared to have been recently cleaned, with two fans set up to blow on it. Investigators also found life insurance policies on Susan Powell and determined that Josh Powell had filed paperwork to withdraw her retirement account money about 10 days after her disappearance.
Anne Bremner, an attorney for the Cox family, said the brother of Josh Powell had said in a deposition that he had driven to Oregon and abandoned a vehicle there. The brother, Michael Powell, committed suicide earlier this year.
The Oregon property that was searched is on a narrow road that juts seven miles into forestland before reaching a dead-end.
"Last couple days have been quite a spectacle with the news media and the helicopters," said neighbor Robert Perkey. "I was up till 1:00 last night with all the commotion and they were back this morning."
Perkey said the people living in the house are renters who moved in recently.
Bremner said she's still interested in seeing more work at the property, including the possibility of having volunteers go to the site to help search.
Cox said he appreciated that investigators spent time on the Oregon search, saying it showed a dedication and determination to find his daughter.