SNOHOMISH, Wash. -- The Snohomish County sheriff's office says searchers have found a body believed to be that of a missing 93-year-old woman from Snohomish.

Sheriff's spokeswoman Rebecca Hover says the body, believed to be Mildred Bird, was found around 4:30 p.m. in a pond in a swampy area southeast of her home in Snohomish.

"They entered the pond, and as they conducted a shoreline water search of the pond is when they located her," said Lt. Rodney Rochon

The cause of death has not been determined, but Hover says there were no signs of foul play. Investigators say it's unclear yet how long she had been dead.

"It was an area that hadn't been searched yet, so this was the first pass through," said Rochon said.

"Grandma on many occasions has gone looking for the cat, and that may have been what occurred," said Bird's grandson John Simpson.

Bird had been missing since Sunday night. Her family says the grandmother went to her home on the family property around 7:30 p.m. on Sunday. When someone went to check on her at 7:30 Monday morning, she was gone.

There were no signs of struggle and all of her belongings were still inside, family members said.

"We called 911 within about ten minutes after we realized she was missing," Simpson said.

Bird's family says there is no medical reason that would cause her to simply wander off.

"There has never been a history of this," Simpson said. "It's just mysterious."

By nightfall on Monday, the search became more urgent. The family members and some 120 volunteers refused to give up the search well past sunset, concentrating on the half-mile radius around her home as Bird does not have access to a car or public transportation. Even kids bicycled through the area, searching for any clues.

"In the last two days I have a whole new appreciation for all my neighbors, and just everybody that's pitched in," Simpson said.

Search dogs were brought in Tuesday, and divers searched local lakes and ponds.

Hover says the Medical Examiner's office has been called and will determine the exact cause of death.

"(She) had a long happy life and this is a sad ending," said Simpson.