A 60-year-old Michigan woman died Friday morning while participating in a grueling two-day, 100-plus-mile endurance run in the mountains of southern Colorado, officials said.

Silverton Medical Rescue, a nonprofit EMS and search and rescue team, said that Elaine Stypula of Farmington Hills was pronounced dead after first responders found her near a lake on a trail in San Juan County, Colo. Her cause of death has not been released.

She had been participating in the Hardrock 100 Endurance Run, an ultramarathon in Colorado’s San Juan Mountains range, in which runners travel 102 ½ miles while navigating rugged terrain with a cumulative elevation change of 66,394 feet, according to the event’s website. The race starts in Silverton and takes competitors through Lake City, Ouray, Telluride and Ophir before returning to SIlverton.

Silverton Medical Rescue said safety team members with the Hardrock 100 called first responders at 9:02 a.m. Mountain Time on Friday and said they were performing CPR on Stypula. The rescue team had to hike a quarter-mile up a “steep, rugged, remote trail” to access Stypula. They attempted to resuscitate her, but she was pronounced dead at 10:27 a.m., Silverton Medical Rescue said in a social media post.

The San Juan County Coroner’s Office later identified the woman as Stypula, an attorney who operated a family law practice in Novi.

A joint press release from the San Juan County Sheriff’s Office and San Juan County Emergency Management Agency attributed her death to an “unknown medical reason.”

“Silverton Medical Rescue is fortunate to have a team of skilled rescue professionals. We support the community, our visitors and each other even on the most difficult calls,” said Michael Burton, incident commander for Silverton Medical Rescue, in a statement.

Stypula was found near Gold Lake on the Little Giant Trail, the rescue organization said. Officials with the Hardrock 100 said more information will be released once the run ends on Sunday.

“The Hardrock 100 Endurance Race has been exceptional in organization and safety throughout the years and an excellent partner to our community,” said Tyler George, director of the Silverton Medical Rescue, in a statement.

“We are deeply saddened to share that a beloved member of our Hardrock Hundred Mile Endurance Run family has passed away during this year’s event. Our hearts are with their family, friends, and fellow runners as we grieve this tremendous loss,” race organizers posted on its website.

According to her law firm’s website, she had competed in multiple Ironman triathlons and ultra-distance runs.

The Hardrock 100 takes participants an average of nearly 40 hours to complete, according to its website. The event “can cause altitude sickness or edema in some runners,” the website states, and “covers extremely rugged terrain including steep scree climbs and descents, snowpacks, river crossings, and boulder fields.”