AEE say the race takes between three and seven hours to complete, depending on weather conditions.
On Saturday, temperatures near Brecon were about 20C.
In a statement, AEE said: “At this immediate time our focus and thoughts are with the family, therefore, AEE, nor I as the March Director will issue any further press release until the family is in possession of the full timeline of events and approve any further messaging.
“Our team is working on this at the time of posting.
“I wish to express my thanks to the Air Ambulance Service, Brecon Mountain Rescue Team and AEE’s Mountain Safety Team for their swift response and professionalism.”
Dyfed-Powys Police said: “We received a call following welfare concerns for a male on Pen y Fan at around 11am on Saturday 4 July.
“Officers attended alongside Mountain Rescue and the Ambulance Service. Sadly, the 68-year-old man passed away. His next of kin are aware and his death is not being treated as suspicious.”