IRVING, Texas -- After raising concerns about the locale of the first National Fantasy Football Convention, the NFL is looking into other events scheduled to be held at venues related to casinos in Las Vegas that will feature active players.

The NFFC canceled its inaugural event that was scheduled for July 10-12 at the Sands Expo after the NFL made the NFL Players Association aware of a long-standing policy that "players and NFL personnel may not participate in promotional activities or other appearances in connection with events that are held at or sponsored by casinos."

The Fantasy Sports Combine is scheduled for July 17 at the Wynn Las Vegas, and current players Brandon Marshall, Shane Vereen, Von Miller and Michael Floyd are billed as making appearances at the event.

Jets receiver Brandon Marshall is among several NFL players billed to make appearances at the Fantasy Sports Combine, scheduled for July 17 at the Wynn Las Vegas. Robert Deutsch/USA TODAY Sports

The Strikes for Kids charity bowling event is July 12 at The Palazzo on July 12. Sammy Watkins, Alshon Jeffery, Aqib Talib and Terrance Knighton are scheduled to attend.

As of now, those events are scheduled to go on as planned, but an NFL spokesperson said the league is looking into them.

Dallas Cowboys quarterback Tony Romo is an investor in NFFC and heavily promoted the event.

He tweeted his disappointment over the weekend that the event had to be canceled, as did several other players who were scheduled to attend. The NFLPA said it is gathering more information before it makes a comment.

More than 100 players were scheduled to appear at the three-day convention that would have paired fantasy-football players with NFL stars, like Rob Gronkowski, Dez Bryant and DeMarco Murray, in question-and-answer sessions.

The league spokesman said the NFL recently became aware of the event and called the organizers to let them know they should move the event to a different location. The NFFC announced its convention on March 24.

Had the players participated in the event, they would have been subject to a fine or suspension, according to a source.

There have been instances in which players have made paid appearances at Las Vegas venues and not gotten in trouble.

Gronkowski hosted his birthday weekend at the Hard Rock Hotel & Casino in May. After becoming a Super Bowl hero, New England Patriots cornerback Malcolm Butler hosted a party at Chateau Nightclub and Rooftop at Paris Las Vegas.

The NFL did not have a comment on those specific examples but wrote via email: "We continue to have conversations with the union to make sure it helps the agents understand these longstanding policies.

These policies are included in the policy manual that each player receives and retains for the season."

There are other alliances between NFL teams and casinos that seem to cloud the league's stance regarding players appearing at promotional events.

The New Orleans Saints will hold training camp for the second straight summer at The Greenbrier Resort in White Sulphur Springs, West Virginia.

There is a casino on-site, but there is no sportsbook. According to the NFL, the Saints made assurances that players, coaches and staff would not be involved in any gambling activity.

In 2007, the NFL began playing regular-season games at Wembley Stadium in London. Betting is allowed elsewhere in the city, but the betting kiosks at the stadium are closed during the games.

Two weeks ago, the Detroit Lions announced a partnership with the MGM Grand Detroit. At $9,500 per ticket, fans are allowed access to a field-level club area that gives them chance to see the team walk into and out of the locker room during pregame, halftime and postgame along with field-level season tickets.

Sports gambling is not available at the MGM Grand Detroit, but is available at casinos in Canada, across the river from Detroit, in parlay form.