Shares of companies with sports betting operations were hit hard after two Major League Baseball (MLB) games scheduled for Monday night were postponed due to a COVID-19 outbreak in the Miami Marlins organisation.

According to figures reported by Market Watch, DraftKings tumbled 8.7%, Penn National Gaming Inc. dropped 6.9%, MGM Resorts International shed 6%, Wynn Resorts Ltd. lost 4.2%, and Las Vegas Sands Corp. fell 2.1%.

DraftKings, who suffered the greatest loss, told Business Insider that “while business in the short term is partially dependent on the sports calendar, we have always said we are playing the long game and will continue our focus on driving a technology-first approach to product innovation in order to keep sports fans engaged.”

The Marlins were due to play their home opener against the Baltimore Orioles, and the Philadelphia Phillies were scheduled to host the New York Yankees. However, both games were cancelled after 14 Marlins players tested positive for COVID-19.

This comes after the Marlins and Phillies played against each other on Sunday despite four Marlin players having contracted the virus. One of these cases was confirmed on Friday, with the other three cases confirmed on Sunday before the match.

Atlanta also hosted the Marlins in an exhibition game before their season opener in Philadelphia, meaning that some Braves players may have also been infected.

Unlike the NBA, MLB teams are traveling to opponent home stadiums, raising concerns about widespread coronavirus outbreaks, with fears that many other games, if not the entire MLB season, could be shuttered if more players test positive for COVID-19.

The MLB was the first major US sports league to resume activity when its season began on Thursday.