Fifteen men and women fell victim to heatstroke Wednesday while running in an "ekiden" relay marathon in Showa Kinen Park in Tachikawa, western Tokyo, shortly after noon. Thirteen were taken to the hospital.
Temperatures in Tachikawa rose to 29.8 degrees at noon at the height of the annual West Tokyo division of the All Japan Citizens' Circuit Marathon. Although the event is held at about the same time every year, the weather was especially hot for mid-September this year, organizers said.
Six men ranging in age from 25 to 56 showed the severest symptoms, which included intense convulsions and dehydration, and required hospitalization, according to Tokyo's fire department.
About 7,200 residents from around the Kanto region ran in the marathon, which is divided into two relay events -- a 23-km course and a 12-km course, both of which are split up among four runners.
Another three people fell ill from the heat at a separate running event in Tokyo's Adachi Ward and were taken to the hospital. They were released soon after.