The bets were made after the sporting events had started.
ESPN reports that the bets were allowed to be placed because incorrect start times were published for a number of Korean and Chinese baseball games due to a manual entry error.
Almost all of the approximately 50 bets were placed using self-serve kiosks at the Bellagio resort between 1.30am and 3am West Coast time. The games in question started at 1am and 2am.
One bet was a $250, 10-leg parlay that paid out more than $137,100. A parlay is a single wager that links together multiple wagers but is dependent on all of those wagers winning together.
The Nevada Gaming Control Board is said to be investigating. Anytime there is a dispute in excess of $500, the state’s books are required to contact the board, which conducts an investigation and makes a ruling by which the books must abide.
“It’s happened to all of us,” Westgate sportsbook director John Murray said. “I think every sportsbook probably since the beginning of time has dealt with this at some point.
“We’ve had past post situations where our employees put in the wrong time or put in the wrong number or they forgot to close something. It’s manual-entry and humans are going to make mistakes.”
The Las Vegas Review-Journal says that Robert Walker, USBookmaking director of sportsbook operations, is still haunted by getting past-posted during his tenure as MGM Resorts sportsbook director from 1996 to 2008.
“I still haven’t gotten over some mistakes I made at The Mirage 20 years ago,” he said. “There’s no worse feeling than when you see a bet come across on a game that’s already started.
“I got lit up on some halftimes before. If you don’t manually close out the halftime line, they keep betting it and that’s what they did.”
Mr Walker said a college football bettor once placed a $3,000 halftime bet on Louisiana State late in the fourth quarter, when the bet couldn’t lose.
“Once I saw that bet come across the ticker in the fourth quarter, I was mortified,” he said.
The sportsbook locked out the ticket from cashing while Mr Walker went to the MGM Grand to explain his mistake to the bettor.
“He gave me the story that they didn’t know and they were LSU fans. But yet you’re watching the game,” he said. “But it was 100 per cent my fault. They were guests of the casino, so at that point I sided with them and it was a mistake we had to eat.”
With reporting from the Associated Press