An NFL probe has found up to 27 New Orleans Saints defenders were involved in a “pay for performance” scheme that included “bounty” payments to those who injured opponents.

The league said an investigation by its security department had discovered the program, which violates league rules.

Investigators found the players received $US1,500 ($A1,394) for a “knockout” hit and $US1,000 ($A929) for a “cart-off” hit. Payments doubled or tripled during the club’s three playoff appearances, according to the league.

Former defensive coordinator Gregg Williams distributed the payments — which were also made for such plays as pass interceptions and fumble recoveries — during the 2009, 2010 and 2011 seasons.

“The payments here are particularly troubling because they involved not just payments for ‘performance,’ but also for injuring opposing players,” NFL commissioner Roger Goodell said in a statement.

Williams, now the defensive coordinator of the St Louis Rams, issued a statement through his new team apologising for participating in the “pay for performance” programme.

“It was a terrible mistake, and we knew it was wrong while we were doing it,” Williams said. “Instead of getting caught up in it, I should have stopped it. I take full responsibility for my role.”

However, former Saints safety Darren Sharper denied that New Orleans players rewarded each other for injuring opponents.

He acknowledged they did have a fund used to pay out for big plays, but told sports network ESPN it was “ridiculous” to say they made bounties on “knocking guys out”.

“Basically all it was is that when a guy gets an interception, then he might get paid,” Sharper said.

League rules ban non-contract bonus payments, and Goodell said he would consider what punishment to mete out.

“The bounty rule promotes two key elements of NFL football: player safety and competitive integrity,” Goodell said. “It is our responsibility to protect player safety and the integrity of our game, and this type of conduct will not be tolerated.

“We have made significant progress in changing the culture with respect to player safety and we are not going to relent.”

Goodell said the probe began in 2010 after allegations that the Saints defenders had targeted Arizona Cardinals quarterback Kurt Warner and Minnesota Vikings quarterback Brett Favre during their 2009 run to the Super Bowl.