The NFL is looking into an arm wrestling contest at the MGM Grand casino in Las Vegas that reportedly featured more than 30 current and former players, including Pittsburgh Steelers linebacker James Harrison and retired running back Marshawn Lynch.

NFL spokesman Brian McCarthy told ESPN on Sunday that the league just became aware of The Pro Football Arm Wrestling Championship and will be looking into it further.

Participating players could be in violation of the league's gambling policy and may face fines. League personnel are prohibited from making promotional appearances at casinos or other gambling-related establishments.

"Had we been asked in advance if this was acceptable, we would have indicated that it was in direct violation of the gambling policy," Joe Lockhart, NFL vice president of communications, told USA Today Sports, which first reported the league's concern over the event. "No one sought pre-approval."

James Harrison, left, and Marshawn Lynch were among the 30-plus current and former NFL players who squared off at the inaugural Pro Football Arm Wrestling Championship, which was filmed at the MGM Grand in Las Vegas this past week. Heidi Fang/Las Vegas Review-Journal

The contest, which took place April 5-9, is scheduled to be broadcast on CBS on May 27-28, with the championship round shown on June 3.

A portion of the prize purses for both individual and team competitions will be donated to charities of the player's choice, according to the event's website. ESPN has reached out to event organizers for comment.

In addition to Harrison and Lynch, Miami Dolphins receiver Kenny Stills, San Francisco 49ers linebacker NaVorro Bowman and Oakland Raiders punter Marquette King were reportedly among the players who participated in the contest.

The arm wrestling contest is the latest test of the NFL's gambling policy, which has been in the spotlight recently with the Raiders' approved relocation to Las Vegas. NFL commissioner Roger Goodell said the Raiders' relocation would not affect the league's gambling policies.

The league has been consistent in regard to events held at Las Vegas casinos. In 2015, a fantasy football convention featuring NFL players, including now-retired Dallas Cowboys quarterback Tony Romo, was scheduled to be held at a Las Vegas convention center connected to the Venetian. In that case, the NFL warned participants that they could be in violation of the league's gambling policy and face potential fines. After the event was eventually canceled, organizers sued the NFL, but the case was later dismissed.