Italian orienteering athlete Mattia Debertolis died on Tuesday after being found unresponsive during competition at the World Games in China's Chengdu, organizers said.
The 29-year-old was discovered unconscious during an orienteering event on August 8 and died four days later, said a joint statement from World Games organisers and the International Orienteering Federation (IOF).
The World Games is a multisport event held every four years for disciplines not included in the Olympics.
"Despite receiving immediate expert medical care at one of China's leading medical institutions, he passed away," the statement said.
It did not provide details on the cause of death.
The event took place in intense heat and humidity, with temperatures above 30 degrees.
Orienteering sees athletes navigate an unmarked course with a map and compass, punching in at designated spots along the route in the quickest time.
Debertolis, from Primiero in eastern Italy, was taking part in the final of the men's middle-distance, the first medal event of the Games.
The six-kilometer (3.7 miles) course featured 180 meters of ascent and 20 control points that athletes must visit.
Footage from the World Games' social media accounts showed athletes running through crop fields and villages on a largely rural course.
The winner, Switzerland's Riccardo Rancan, completed the course in 45 minutes and 22 seconds.
"I needed to acclimatize quickly with hot and humid conditions. I think I managed quite well," Chinese state media quoted Rancan as saying.
Debertolis was listed as "Did Not Finish" in official results, along with 11 other athletes.
Black armbands
He was ranked 137th in the men's Orienteering World Rankings and had been competing since 2014, according to the IOF website.
He participated in several World Championships and World Cups as part of the Italian team.
Alongside his training, Debertolis was studying for a PhD at the KTH Royal Institute of Technology in Stockholm, where he lived.
President of the Italian Orienteering Federation (FISO), Alfio Giomi, invited the national team to wear black armbands while competing in the World Mountain Bike Orienteering Championships, which begin on Tuesday in Poland.
Debertolis' family had agreed that "athletes will be able to participate in the competitions in Mattia's name and memory", Giomi said in an online statement.
World Games organizers and the IOF were "struck by this tragedy and extend their heartfelt condolences to the family and friends of the athlete and the whole orienteering community", the joint statement read.
"Our thoughts are with those touched by this event."
Organizers will "continue to support the family of Mattia Debertolis and the orienteering community in every possible way", it added.
This is the 12th edition of the World Games and it runs until August 17, with approximately 4,000 athletes competing in 253 events.
