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Authorities in North Yarmouth, Maine, Wednesday spent a third day searching for an elementary school teacher whose husband said she disappeared with only some missing footwear to show for it.

Jay Westra said his 47-year-old wife Kristin must have slipped out of their home in the darkness of the early morning hours after she said she recently had trouble sleeping.

"She expressed that she had had some sleepless nights and was worried," Westra told NBC News.

In fact, Westra said, his wife had gone to see a "licensed clinical nurse practitioner" Sunday, the day before she was reported missing. Westra said he's a pediatric oncology nurse at Maine Medical Center's Children's Cancer Program.

"There was a safety assessment and Kristin was not at risk for any harm to herself or anybody else," he said.

Kristin Westra was captured on a neighbor's security video camera returning home from a jog about 6 p.m. Sunday, according to NBC News affiliate WCSH. Her husband said she turned in at 8 that night.

He awoke at 3:30 a.m. Monday, checked his phone, and noticed that Kristin was not in bed. "I thought maybe she had gone to another room to another bed to sleep," he said.

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Later, Jay Westra said he noticed that a back entrance to their home "was slightly open." "She may have left the back door [open] not trying to wake anybody up," he said.

Westra said it would have been odd for his wife to wonder off overnight. He said that although she had "trained for many marathons and half marathons" it would have been abnormal for her to try to run on a cold, rainy morning before the sun rose.

What's more, he said, he believes some footwear is missing — "either a pair of running shoes or a pair of flip flops that are not here."

He got into his vehicle and drove to familiar areas of town in an effort to find his wife, but ultimately Westra enlisted the help of authorities Monday, he said.

Friends of the teacher set up a website to solicit information on her wherabouts.

Her brother said on Facebook that "we are getting swamped with calls and texts" from well-wishers but that "all we can do right now is give our support and love to Jay Westra" and the couple's children, a 10-year-old daughter and a teenage stepson.

"I told my daughter that sometimes adults have stress or worries or anger and just like she would, sometimes adults need time to think," Westra said.

Capt. Scott Stewart of the Cumberland County Sheriff’s Office said eight detectives as well as Maine State Police and the Maine Warden Service have been enlisted to help search for Kristin Westra.

"We're searching everywhere that we may think she may be, may have gone, may have liked," the captain said. "We're still investigating this as a missing person, looking for a positive resolution."

Stewart called Jay Westra "more than helpful. More than anybody would expect."

Game Warden Corporal John MacDonald said in a statement Wednesday that the search had gone off-road.

"Nearly 50 trained search crews, K9's, ATV’s and drones were used to cover varied terrain that included wetlands, thick forest and open fields," he said.

"Still no clues have been provided or detected to indicate Westra is in the woods," he said.

"Her vehicle and other personal belongings were left behind at the residence," he added. "This remains the only clue that Kristin Westra might be near her North Yarmouth home."

Jay Westra urged his wife to "come home" and said that whatever prompted his wife to go missing can be overcome.

"We've always taken care of everything," he said, "and solved every problem."