Police and residents are combing through the town of Sidney, Montana, in hopes of finding a teacher who went missing after going for a morning run, leaving behind no trace besides a lone shoe, the city's police chief told CNN.

Schoolteacher Sherry Arnold, 43, left her home Saturday morning for a run along her normal path, but she never returned, Sidney police Chief Frank DiFonzo said.

DiFonzo said that teams have been searching areas around the eastern Montana town since Arnold's disappearance using dogs and aircraft. He said the National Guard was also assisting.

Police described Arnold as 5 feet, 10 inches and 140 pounds with black hair. She was last seen wearing a blue sweatshirt with a white stripe and red nylon pants with black leggings.

Police are looking into different scenarios regarding Arnold's disappearance, but they believe she may have been abducted or possibly hit by a vehicle, DiFonzo said.

"Everything's accounted for, her personal things, her vehicle is accounted for," Bob Burnison, the assistant police chief, told CNN affiliate KRTV-TV in Great Falls. "We just feel that there's something drastic, either happened to her or something to that effect, why she wouldn't have made contact back."

The police chief said there was no evidence the shoe remained behind after an animal attack, one scenario that residents had been floating.

Christine Mullen, 26, a CNN iReport contributor, said that she went to the site of one of the searches, where thousands turned up to help.

"We've got horses going out and ATVs and people just going out on their own," Mullen told CNN. "There's a lot of pasture, dirt roads and farmland to cover."

Mullen said she doesn't know Arnold but she feels the impact of her disappearance.

"In this community when something like this happens, it's not just a small thing where a few people are involved," Mullen said, adding that some employers are even allowing people to leave work to take part in the search. "Everybody is involved."

Mullen's iReport about Arnold attracted strong response from readers, including pleas from residents to help search and bring the teacher's disappearance to light.

Facebook group: Help find Sherry Arnold

"We're such a small community, and crime is absolutely unheard of," Mullen said. "We don't lock our car doors. (We're) completely shocked."

Police said they will continue to search for clues.

"We're going to keep going until we can get some answers here," Burnison told KRTV. "We just want to find her, you know. Our hope is she's OK."