Two runners died near the finish line of a half marathon in Raleigh on Sunday, WLOS-TV reported.
Officials with the Rock 'n' Roll Marathon said both deaths appear to be from natural causes.
"We regret to confirm that two participants passed away at today's half-marathon," said Dr. P.Z. Pearce, the event's medical director.
Pearce said doctors and race organizers have spoken with the families of the runners and asked for privacy. The names of the runners, both men, have not been released.
According to WLOS, a 35-year-old man collapsed near the 10- and 11-mile markers and a 31-year-old man died near the finish line. Both were taken to hospitals and pronounced dead.
Dr. Jeff Bytomski, head medical team physican at Duke University, told The State he spoke with doctors at race "and they do think it's cardiac, which is the most common reason" for runners to die at races.
"It's just an inherent risk at these races," he added. "It's still a very low risk, but it happens."
The event, which features a full marathon and half marathon, included 12,000 runners. Since 2005, a total of 12 runners have passed away during the event, though marathon deaths are statistically uncommon.
In 2012, a study published in the New England Journal of Medicine found that of almost 11 million marathon participants between 2000 and 2011, there were 59 cardiac arrests, and only 42 of them fatal.
Additionally, more than 85 percent of the heart attacks occurred in men. In 23 of the deaths that medical researchers could investigate, 15 were found with abnormal thickening of the heart skin muscle and nine suffered other cardiac abnormalities.
Alex Granados of the North Raleigh News was waiting for his brother to cross the finish line when one of the men collapsed near him.
"All of a sudden, some people in line started calling for a medic. A guy had collapsed about a hundred yards down from me," Granados said. "The paramedics came and spent 10 to 20 minutes furiously doing chest compressions. After a while, they got him on a gurney and wheeled him by me."
