The Brisbane Race Club and electricity supplier Energex have launched a joint investigation into the power outage at Eagle Farm racecourse on Melbourne Cup day.

More than 10,000 punters were literally left in the dark when power to the course failed between 1pm and 3pm on Tuesday with patrons unable to see the Cup.

BRC Chairman Neville Bell said he felt deeply for racegoers and it had been equally devastating for his staff who had spent months planning the event.

"At this stage I can't say exactly what went wrong. Basically the outage seems to have been outside the track when some mechanisms blew out, but what caused it I don't know just yet," Bell said.

"Energex were the only ones who could fix it and they did that. But it took time and at least we could finish our nine-event race program."

Bell said there were many theories being put forward but he would prefer to wait until the inquiry was finalised.

"It isn't the first time we have had 10,000 people at Eagle Farm. We had 20,000 on Stradbroke day this year and I am told we were actually using more power on Tuesday than that day," he said.

"We have upgraded a lot of our electrical equipment such as fridges, air conditioning and the like."

He said the club had recently spent $180,000 upgrading the on-course power box.

Bell said he had been asked why the club did not have a back-up generator.

"The simple answer is we couldn't get one big enough," he said.

"But there is a new mobile generator coming on the market and we will be looking at that."