A woman has died after taking part in a 10-mile endurance race in the Scottish Borders.

Emergency crews were called to the Mighty Deerstalker event at Innerleithen in Tweeddale after the woman, 48, became unwell just before 6pm on Saturday. She died en route to Borders general hospital.

A spokesman for Rat Race Adventure Sports, the event organiser, said: “We are extremely saddened to confirm that a participant in our Mighty Deerstalker event passed away yesterday. A member of our medical team was on the scene within three minutes as we implemented our response protocols. They were assisted by an off-duty paramedic until the arrival of the Scottish ambulance service.

“Tragically, we have since learned that the individual passed away en route to hospital. Rat Race Adventure Sports will give full assistance to the appropriate authorities. Our heartfelt thoughts and condolences are with the family and friends of the deceased.”

In the event, now in its 11th year and billed as the UK’s biggest night race, hundreds of participants tackle off-road terrain while wearing head torches. On its website, the organisers state: “The Mighty Deerstalker is as tough as it gets; hills, mud, swamp, darkness, rivers, obstacles and always devilishly vague on the true distance, this event never disappoints but it often hurts.”