Leiden’s annual marathon was abandoned at the weekend after 25 runners were taken to hospital suffering from the effects of heat exhaustion.

City mayor Peter van de Velden decided to stop the race at 3pm, amid concerns that local hospitals were struggling to cope with the number of casualties.

Most of the 1,750 runners had finished the race, which began at 10am, but those still out on the course were asked to walk to the finish. The last participants were roundly applauded as they crossed the line at around 4pm.

Another 6,500 people started the half-marathon race at 11am. The 10K race, which had been due to start at 2.30pm, was abandoned.

Some 15 runners were taken to the LUMC hospital in Leiden, while another 10 were treated at the Alrijne Ziekenhuis in Leiderdorp. All of them were discharged later in the day.

Rising temperatures

A spokesman for the Hollands Midden safety board said authorities decided to suspend the race because the hospitals risked becoming overburdened as temperatures reached 25C.

“Too many people were falling ill,” Van der Velden told Omroep West. “The pressure on ambulances, hospitals and other emergency services was too great, which left us with no choice. People’s health and safety comes first.”

Organiser Tjeerd Scheffer said runners were caught out by the sharp rise in temperatures in recent days, having trained in relatively cool conditions for the time of year.

“It’s busy and warm, so it’s not unusual that people had trouble in the heat,” he said.

But the two hospitals said the number of casualties was “manageable” and they were operating well within their capacity.