Organizers Run 4 Wales said the deaths were the first fatalities in the race's 15-year history. Chief executive Matt Newman said: "This is a terrible tragedy for the families. Our deepest sympathies go out to their family and friends.
"The emergency services reacted to this terrible situation with great speed and professionalism. Everyone connected with the race is devastated." The victims have not yet been named. Some media reports said they were men — and in their 20s and 30s.
This year's edition of the race attracted 25,000 competitors. Australian runner Jack Rayner won the men's race in the Welsh capital, while Juliet Chekwel of Uganda was first in the women's event.
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