This week’s official announcement of the Floyd Mayweather-Conor McGregor fight generated a flurry of betting action that caused Las Vegas sportsbooks to significantly trim the odds on the favorite and left them holding lopsided action on the underdog from the UFC.

When the fight was announced Wednesday, Mayweather, an undefeated boxing champion, was listed as a minus-1,100 favorite. But by Saturday afternoon, Mayweather’s odds had nearly been trimmed in half, down to minus-600 at some shops, as books were flooded by small bets on McGregor.

At Caesars Palace sportsbooks, 140 of the first 144 bets were on McGregor, who was paying back around 5-1. Almost all of the early action was small and placed by recreational bettors. One sportsbook manager described it as “square-a-palooza.”

“Everyone and their cousin wants action on this fight,” the sportsbook manager told ESPN in an email.

More money had been bet on Mayweather-McGregor in the past two days at Caesars Palace than had been bet over the past month on the title fight between Sergey Kovalev and Andre Ward that is slated for Saturday night.

The bets on Mayweather, however few and far between, have typically been larger than the bets on McGregor. The Westgate SuperBook took a $50,000 bet on Mayweather on May 30, two weeks before the fight was made official, and CG Technology took a $45,000 bet on Mayweather on Thursday.

At the Westgate, 90 percent of the bets were on McGregor, but 79 percent of the money was on Mayweather.

On Saturday, the Westgate released odds on the method of victory, with Mayweather by knockout a hefty favorite at 5-9. Mayweather by decision is listed at 2-1, followed by McGregor by knockout at 6-1. McGregor by decision pays 30-1.

Mayweather-McGregor will take place Aug. 26 in Las Vegas.