Officials with the Denver Broncos warn of fraudulent ticket sales in anticipation of Sunday's home opener.7NEWS has learned approximately 20 to 30 people are turned away per game using tickets that they had no idea were fake."You may not know until you get to the turnstyle," said director of ticket sales Kirk Dyer. "With Peyton being here, you know first game of the year, playing the Steelers, Sunday night football, there's a high demand for our tickets," he said.7NEWS asked how can you prevent a costly fumble. The team says the only way to guarantee a genuine ticket is to buy it from the team's ticket office, ticket master or the NFL Exchange online. They say you can't necessarily spot a counterfeit ticket.That's why Rebecca Pellican buys directly from the source. The team can't guarantee the authenticity of tickets purchased online or through ticket brokers."Come straight from the Broncos' ticket office, we feel very confident they're legit," said Pellican.If you've purchased a fake ticket, the Broncos will not offer a refund. Officials say this is a case of buyer beware.