Hundreds of running competitors raced themselves off the map after the lead athletes followed a cyclist who had been mistaken for a race official.
Runners in the Heaton Memorial 10k race, which took place on Newcastle Town Moor, had run about half a mile before chaos ensued.
A cyclist, who was wearing a hi-vis jacket, was mistakenly followed by the runners which took the whole event off course.
Competitor Paul Smith told the Northern Echo: "In all the years I have been running races I have never come across anything quite like it."
The runners were eventually brought back to the start line and the race began again.
A statement from the Heaton Harriers committee on their website said: "As runners at today's event will be aware the race had to be restarted due to the lead runners taking an incorrect route as they approached the lake.
"As a result most athletes ran around 800m before they were called back to start the race again.
"This was due to a member of the public entering the course on a bicycle just before the starting gun was sounded.
"The cyclist was dressed in fluorescent clothing and as the leading group of runners ran closer to him they mistook him to be a race official and mistakenly followed him to the right instead of carrying straight on.
"We apologise for any inconvenience caused and will take steps in future events to ensure this does not happen again."