Two of the competitors who collapsed during the Great North Run died from natural causes, a coroner said today.

Medical examinations revealed that deputy headteacher Phil Lewis and company director Reuben Wilson - the youngest of the four men to collapse during the famous half-marathon - both died from natural causes. Post mortem examinations are due to be carried out on 34-year-old Kieran Patching, of Chatham, Kent, and David Mahaffey, 43, from York, later today.

Fellow competitors in the race, which begins in Newcastle before crossing the Tyne Bridge into Gateshead and finishing in South Shields, complained of the heat.

The PA WeatherCentre said temperatures reached 18C (64F) on Sunday - several degrees higher than the average for September.

Ambulance officials said ''warm weather and sunshine'' may be the reason for the deaths and medical staff reported a higher number of people needing treatment than in previous years.

Sports Minister Richard Caborn said the advice given to athletes taking part in large running events might need to be updated, emphasising the importance of drinking enough water.

Organisers of the annual 13-mile road race, which was celebrating its 25th anniversary, said a sophisticated medical plan was in operation to help any of the 38,000 runners.

Glowing tributes were paid to Mr Lewis, who had taught at Moorside Community Technical College in Consett, Co Durham, for 26 years.

Mr Lewis, 52, from Chester-le-Street, leaves a widow, Rose, and two grown-up children and was described as an ''inspiration to staff and pupils''.

The family of Mr Wilson, 28, from Leeds, spoke of the shock of his sister, who was also running the race, witnessing the desperate attempts by medical staff to save his life.

A spokeswoman for the South Tyneside and Gateshead coroner, Terrence Carney, said: ''A post-mortem examination revealed Mr Lewis died from natural causes and it was unfortunate he died while competing in the Great North Run.

''There will not be an inquest into Mr Lewis's death and his body will be formally released to his family later today.''

The spokeswoman said that Mr Wilson was also likely to have died from natural causes but further tests would be carried out.

''The death of Mr Wilson is looking very much like natural causes as well and because of his young age, the doctor wants to carry out a few more tests,'' she said.

''The coroner will open an inquest in private today so these tests can be carried out and the body can be released to his family.''

The spokeswoman said it was unlikely that an inquest would be held into Mr Wilson's death.

She added: ''When we get the report back from the pathologist, we expect the results to be natural causes and it will be a case of the coroner signing the paperwork.''