Other concerned neighbors - mostly strangers to the missing woman - got into their snowmobiles and fanned out across frozen farmland, hoping to find something that might reveal the whereabouts of Dru Sjodin.
Law enforcement agencies also conducted smaller searches based on a few of the nearly 900 leads authorities have received in the disappearance of the 22-year-old, who lived in Pequot Lakes, Minn., and worked in Grand Forks, North Dakota.
"We're gonna find you Dru, keep hanging on," said Sjodin's brother, Sven, at a news conference Sunday. "We're just around the corner from you and we know we're gonna find you."
Divers from as far as New York and Los Angeles searched the area's rivers and streams, and the U.S. Border Patrol searched by air.
Sjodin was last seen in the late afternoon on Nov. 22 at the Columbia Mall in Grand Forks, where she was shopping after finishing her regular shift at the Victoria's Secret store in that same shopping center.
Police believe Sjodin may have been abducted while she was talking to her boyfriend on her cell phone. He has told authorities that he was talking to her on her cell phone when the conversation abruptly ended after she said "Oh, my God" or "Oh, no."
Sjodin's car was found in the mall parking lot, and police have said there was no sign of a struggle.
Authorities also say that a forensic examination of the car has not yielded any major clues.
Although Sjodin remains classified as a missing person, "Everything I've heard, everything I've seen leads me to believe that she was (abducted)," says Grand Forks police Sgt. Michael Hedlund.
The U.S. Border Patrol has been doing airborne searches of the region, and as of now, about 30 FBI agents are working on the case. So are investigators with 20 different agencies from three states and the Canadian province of Manitoba.
Hedlund says authorities have been interviewing some individuals described as "people of interest" but none are being called suspects.
About 150 volunteers helped search a swath of Grand Forks farmland Sunday morning, but authorities would not say why the area was singled out.
One focus of the search has been the area in and around Fisher, Minnesota, because a second call from Sjodin's cell phone - on Saturday night - was traced to an area within five miles of the Fisher's Landing rest area, near Fisher on U.S. Highway 2.
That's about 12 miles east of Grand Forks.
According to her family, the second call from Sjodin's cell phone - again, to her boyfriend - lasted only about a minute. No voice was heard, but there was the sound of sound of static and numbers being punched in.
The boyfriend later called Sjodin's roommate to ask about her, and the roommate called police when Sjodin failed to show up for her 9 p.m. shift as a waitress at a Grand Forks bar.
Everyone living or owning property near Fisher has been asked by police to personally check the land and buildings they own for any possible clues.
Sjodin is described as 5'5" tall, 130 pounds, with blue eyes and frosted blonde hair. She was last seen wearing a pink and purple V-neck blouse, black pants, black blazer, black loafers and a black pea coat, carrying a small black purse.
The reward being offered for Sjodin's safe return is now up to $140,000. A fund has been set up at Lakes State Bank in Pequot Lakes, Minn., where Sjodin graduated from high school.
Her unexplained disappearance has set nerves on edge in the Dakotas and Minnesota.
In Grand Forks, retailers said supplies of stun guns and pepper spray are selling fast.
"I'm sure there's a lot of scared young women right now," said Greg Washburn, manager of the camping supplies department at Cabela's.
Sjodin's family has set up a Web site www.finddru.com to appeal for volunteers, distribute posters and buttons, and otherwise get out the word on the search.
Anyone with information on Sjodin's whereabouts is asked to call police in Grand Forks at 701-787-8000, call the tips line at 701-780-8213, or e-mail: firstname.lastname@example.org.