PORTLAND, Ore. — Kyron Horman's mother talked about developments in the case of her missing son and announced that she's writing a new book about him during an emotional press conference Tuesday morning.

Desiree Young spoke at Tualatin Valley Fire & Rescue Station #72 in Portland on Tuesday, the nine-year anniversary of Kyron’s disappearance from Skyline Elementary School in Portland. He was 7 years old when he disappeared on June 4, 2010. He has never been found but investigators say the case is active and ongoing.

Young said Tuesday that authorities have narrowed the search area for Horman to less than 100 acres.

"It's a huge amount of progress, with the all the searches that we've done. We've been able to get to a point, where at least I feel better," Young said. "I don't look at all those rolling hills and think, 'We're looking as far as the eye can see.' We're not. We're looking in key areas, and we've narrowed it down."

Young said she couldn't reveal where the search has centralized.

"I can't say that. Law enforcement would get very angry at me," she said.

WATCH: Kyron Horman's mother speaks 9 years after son's disappearance

“The case is very active,” Young told KGW. “It has been a flurry of activity.”

Young said police have "new evidence" related to computer and phone activity. She confirmed law enforcement has conducted several searches in the past nine months at undisclosed locations.

"We've got new technology," Young said. "Things are changing all the time."

Young also announced that she has been working with best-selling author Rebecca Morris to write a book about the disappearance of her son. The new book, titled "Love You Forever – The Search for Kyron Horman," will be published later this year.

RELATED: Kyron Horman’s mom to release book, shares new details about investigation

Young said any money she receives from the book will go to a nonprofit that aims to help missing children and their families.

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The National Center for Missing and Exploited Children released a new age-progressed image of Kyrone Horman on Thursday, May 25, 2017. (Photo: National Center for Missing and Exploited Children)

A KGW investigation in 2017 revealed that the Multnomah County Sheriff's Office was coordinating ground searches and detectives were analyzing new computer evidence. A grand jury continues to hear evidence in Kyron's disappearance and has met multiple times.

VIDEO: Kyron Horman timeline 

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