The TAB was forced to abandon betting and refund money to punters after a worker failed to close betting lines on a $65,000 novice horse race.
At least 25 people had noticed the glitch during the Singapore race 5, novice 1200m at 1.20am (NZ time) yesterday morning and had placed a high number of winning bets on New Zealand-bred galloper Blue Swede.
A Hastings-based punter, who did not want to be named, said he'd placed a bet on the winning horse because dividends had started rising before the race.
"I noticed after the race they normally say dividends were now paying on such and such and that never happened," he said.
"I thought it was crazy, I've never seen this happen before. Overall it was quite strange."
Michael Dore, head of totalisator betting at TAB, said there had only been three incidents in the last five years where betting had accidentally remained open due to human error.
"Generally, it's been 15 to 20 seconds into the race that a person has been distracted or held up on the phone where they've missed the start, which isn't quite so fatal because the race hasn't concluded," said Dore. "But this one, as you can imagine, two minutes after the horses had crossed the finishing line is as bad as it gets."
Dore added that all the precautions and alerts warning the worker the race was about to start were missed.
"The operator knew they made a mistake and they fessed up straight away which is the right thing to do, it's not something you can sweep under the carpet," said Dore.
The TAB will meet with the worker tomorrow to investigate what happened.
Dore said that the priority yesterday was to refund all the money placed on the race back to customers, including those who had bet on the winning combinations.
"It looks pretty ugly and obviously being very late at night we had the security of knowing virtually all of the bets placed on the race were placed via account bets, which means we can just deposit it straight back to them."