Four men died while taking part in the 25th Great North Run, police have confirmed.
The men were among around 50,000 people running the 13- mile course from Newcastle, across the famous Tyne Bridge to Gateshead and on to South Shields in a bid to raise around £10 million for good causes. Police said there had been no major incident and the deaths were unrelated.
Many of the runners in the race reported feeling extremely hot as temperatures soared in the North-east.
A Northumbria Police spokesman said: "Four male participants have died and all the relatives have yet to be told so no further details will be released at this time."
A spokesman for the run organisers said: "We would like to express our deepest sympathy and sorrow for their families."
The organiser's spokesman said the event was expected to raise around £10 million for charities and good causes.
He said: "It's a huge event with immense coverage, both nationally and internationally, which does a lot for good causes.
"But we are all upset that this has happened. Our sympathies go out to all the families and friends of those involved."