(CNN) -- Kyron Horman has been missing since June 4, 2010, but his mother is not giving up.

Desiree Young and volunteers spent "two solid days of searching" for her son this weekend, she said in a news conference Sunday in Portland, Ore., calling the search "successful."

More than 100 volunteers, along with 10 search dog teams from around the country, joined the search effort in the Portland area, looking for evidence that might help solve Kyron's disappearance.

Kyron was 7 years old when he went missing. He was last seen by his stepmother, Terri Horman, who told police she had dropped him off at his school, Skyline Elementary.

Young was optimistic about the latest search, telling reporters, "we found a lot of things, and possibly evidence," but declined to give details, citing the ongoing criminal investigation. Everything searchers found will go to law enforcement for further examination, she said.

Though Portland law enforcement was not part of this search, Young said she has been working closely with police and has been keeping them informed.

The Multnomah County Sheriff's Office told CNN affiliate KGW that their investigation is ongoing, and they hope the volunteers find something that helps bring Kyron home.

Since Kyron's disappearance, most of the speculation has focused on the boy's stepmother.

In August 2010, investigators solicited the public's help for information about the location of the white pickup truck that she is believed to have driven the morning of Kyron's disappearance.

And in divorce filings, the boy's father, Kaine Horman, said he believes his estranged wife, Terri Horman, "is involved" in the boy's disappearance.

No charges have been filed against anyone in the case, nor has anyone officially been named a suspect.

Young told the media gathered Sunday that she will not give up searching for her son.

"My mission has always been to bring Kyron home, and I will go to the ends of the earth to do that."

Jennifer Moore contributed to this report.

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