The well-known hiker whose body was found on Mount Rainier over the weekend died of hypothermia, the Pierce County Medical Examiner’s Office said Monday.

Karen Sykes, 70, of Seattle, had been reported missing late Wednesday when she failed to meet up with her boyfriend as planned during a day hike in the Owyhigh Lakes area near Mount Rainier.

Mount Rainier National Park officials suspended a three-day search for her on Saturday when they discovered the body of a woman in their search area near the eastern branch of Boundary Creek in rough, steep terrain.

Sykes’ daughter Annette Shirey said Monday that park officials had informed her they’d found her mother’s body, according to The Associated Press.

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A secondary cause of Sykes’ death was heart disease, according to the Medical Examiner’s Office. She did not have other injuries, and officials ruled her death accidental.

Despite the autopsy finding of heart disease, Sykes’ daughter and others said she was healthy and fit, and often hiked twice a week.

While not certain of the circumstances of her death, those who knew Sykes said earlier that it could have happened to anyone, no matter how experienced in the outdoors.

“The mountains are big. There’s a lot going on. She was extremely experienced, but experience has nothing to do with any of it,” said Kim Brown, who hiked with Sykes.

Sykes was well-known in the Northwest hiking community. She wrote stories about hiking for online publications and newspapers, authored a guide book about Western Washington hikes and co-wrote another book about hikes in wildflower areas. She wrote a popular trail column in the Seattle Post-Intelligencer and produced additional stories about Washington treks for The Seattle Times.

She kept a blog called “Karens Trails” where she posted hiking-related stories, photographs and trail reports. Her last post was on June 4, when she wrote about the Lime Kiln Trail in Snohomish County.

“Though I’m not young I still enjoy the challenge of rugged trails, obscure trails, abandoned trails and looking for artifacts even if the price is a losing battle with Devil’s Club, salmonberry, rotting stumps and nettles,” Sykes wrote. “Sometimes it just feels good to tussle with Mother Nature; it builds character.”

Material from Seattle Times reporter Paige Cornwell and The Associated Press was included in this report.