A 33-year-old man died from a heart attack while trying to complete the Mexico City marathon over the weekend, a source close to race organizers told Efe.
Juan Pablo de la Mora died Sunday while competing in the 42-kilometer (26.2-mile) race.
Mora was one of the 9,000 runners, the majority of them amateurs, who took part in the race.
The runner collapsed at an undetermined point in the race and later died.
The Mexico City marathon takes place at an altitude of 2,240 meters (7,344 feet) above sea level, but the course is almost entirely flat.
The weather was pleasant on Sunday, with temperatures rising later in the day but never reaching extreme conditions.
Kenya's Peter Nkaya won the men's race with a time of 2:15:53, while Ethiopia's Alene Amare was victorious in the women's race with a time of 2:38:50.
The Mexico City marathon is one of more than 600 races held annually in Mexico and is considered, along with the Torreon, Monterrey and Mazatlan marathons, to be among the top events at this distance in the country. EFE