A runner at the Cocodona 250 ultramarathon in Arizona has died after a medical emergency, organizers said on Tuesday.

According to a statement posted on Instagram, a participant experienced a “serious medical emergency” during the 253-mile endurance race, which began Monday and continues through Saturday.

“Out of respect for the runner’s family and loved ones, we are not sharing additional personal details at this time,” the statement said. “Our team is supporting those directly involved and will share more only when appropriate.

“Please keep the runner’s family, friends, fellow runners, volunteers, and first responders in your thoughts. We are deeply grateful to this beautiful community.”

Organizers said the race will continue in the runner’s honor and asked participants and crew “to carry the memory of this runner with you on the trail”.

The Cocodona 250 has been held annually since 2021 and stretches from Black Canyon City, a town 20 miles north of Phoenix, to Flagstaff. Its organizer, Aravaipa Running, says the course links “some of the most iconic trails and towns in Arizona”.

The course begins in the desert and involves an estimated 38,791ft of elevation gain, with a high point of 9,241ft outside Flagstaff. The race tracker listed nearly 400 participants.

The top finisher in last year’s event, American Dan Green, ran a course record of 58 hours 47 minutes 18 seconds. Fellow American Rachel Entrekin was the top runner on the women’s side, finishing in 63:50:55, also a course record.

Entrekin led this year’s race through 48 hours, according to Run by Outside, and is attempting to become the first woman to finish first overall.

In 2025, a runner died after collapsing during a 102-mile endurance race through the Colorado mountains. Four years earlier, 21 competitors died during a 62-mile ultramarathon in China amid freezing mountain conditions, raising concerns about safety in the sport.