During last year’s Hong Kong marathon, a woman taking a picture of herself at the starting line caused a pile-up of runners when she dropped her phone and bent over to pick it up as the race began.

"The problem was that a number of runners were trying to take self-portrait pictures using their smartphones. What we are trying to do is to encourage people not to do that," the marathon’s chief executive, Benjamin Hung Pi-cheng, said.

Safety, of course, is the organizing committee’s paramount concern. Last year’s winner was able to win despite being part of the pile-up, but another event like that one could turn out far worse. Deemed an “anti-selfie” campaign by many media outlets, the marathon's photo ban was announced at the same time as arrangements were announced for the races on Monday. About 73,000 runners will participate.

“For the race itself we will have officials hold some message boards to remind people not to take photos at the start, on the route or at the finish because it is dangerous,” William Ko, chairman of the marathon’s organizing committee, told Agence France-Presse on Tuesday.