Two runners competing in the Rock 'n' Roll Half Marathon in San Jose have died.
Medical personnel were unsuccessful in trying revive 35-year-old Brandon Whitehurst of Antioch and 34-year-old Rose Lo of South San Francisco during the Sunday event.
Race medical director Dr. Lewis Maharam said the losses were "unfortunate and tragic."
The Santa Clara County Coroner's office said it has not yet determined how the runners died.
Over 10,000 runners participated in the 13.1 mile race through San Jose, where temperatures reached a mild 68 degrees.
Event spokesman Dan Cruz said these were the first deaths in the race's 3 year history.
At a Rock 'n' Roll Half Marathon in Virginia last month a 23-year-old male runner died.