Family Searching for Missing Oregon Mom

— -- The family of a missing mom in Oregon has launched a massive search for the woman who police say was last seen at a gas station four days ago.

Volunteers are furiously searching for Jennifer Huston, whose face is plastered on posters at shopping centers along Interstate 5 near Portland, after police say they exhausted all their leads.

Huston's husband, Kallen Huston, is grateful for the help and is pleading for her safe return.

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He says there's no reason his wife would leave her family on her own will. The couple have two sons, ages 2 and 6.

"She wouldn't leave all of us. She just wouldn't do this," he told ABC News. "Everybody who knows her agrees."

He described Huston, 38, as a "devoted" stay-at-home mom who was involved in her community and her older son's school. She disappeared after leaving the family's Dundee home on July 24 to run errands, her husband said.

"I have asked all of her close girlfriends, is there anything that I didn't know about her as a husband that I should have known about?" he added. "Was she upset with me and I was just clueless to the fact? And everybody says the same thing -- everyone who is really close to her, and I truly believe this -- she would not do this."

Newberg-Dundee Police Captain Jeff Kosmicki said surveillance video shows Huston buying gas on Thursday evening at a Circle K gas station in Newberg. She was driving a dark green Lexus LX-470.

The search continues, but he told The Associated Press police have exhausted all of their leads.

Huston's mother, however, suspects foul play.

"This isn't normal, so, my guess would be something -- something is not right," Deborah Turner told ABC News. "Somebody has to have her because she wouldn't do this. And it is a thought you don't want to think about, but I'm pretty sure that somebody has her. She would call. She would escape. She would fight to get out of there."

Huston was last seen wearing black and pink Nike sneakers and black yoga pants, according to a flier her family created. She is 5-foot-7-inches tall and has shoulder-length blond hair and blue eyes.

The family is offering a reward for any information that leads to Huston's return, according to the Facebook page, "Find Jennifer Huston."

Kallen Huston said nothing out of the ordinary had occurred before his wife went missing, except that she had been experiencing headaches. He begged for her to return if possible.

"We love you, please come home if you can," he said, choking up. "If you are being held against your will, stay strong, we are fighting every angle we can to find you. I love you. The boys love you and they miss you, and I miss you. We are going to find you."