For the second time in two years, a San Francisco 49ers fan has died after suffering a medical emergency at one of the team's games, as a man suffered a fatal heart attack during the inaugural football game at Levi's Stadium Sunday afternoon.

The Santa Clara Fire Department told the Associated Press that stadium staff responded to a cardiac emergency during the third quarter of the 49ers' preseason home opener against the Denver Broncos.

The man received CPR and was rushed to a hospital, where he was pronounced dead. His name was not released.

The 49ers issued a statement Sunday night offering condolences to his family and friends.

The team's 34-0 loss to the Broncos and 80-degree heat drove thousands of fans to leave the new stadium midway through the game.

Team officials told the San Jose Mercury News there was an unusually high number of calls for emergency services, likely because of the heat.

Last September, a 49ers fan died after falling from an elevated walkway during the team's season-opening game against the Green Bay Packers at Candlestick Park, the 49ers' former home stadium. 

The Associated Press contributed to this report.