NEW YORK >> Encouraging defensive players to be aggressive, hit hard and not back down is standard procedure in pro football. Paying them to injure the opposition is not.

New Orleans Saints players and at least one assistant coach, defensive coordinator Gregg Williams, maintained a bounty pool of up to $50,000 the last three seasons, the NFL said Friday. Payoffs came for inflicting game-ending injuries.

Among the targets were Brett Favre and Kurt Warner, with "knockouts" worth $1,500 and "cart-offs" $1,000. Payments doubled or tripled for the playoffs, and, according to an investigation by NFL security, pool amounts reached their height in 2009 — the year the Saints won the Super Bowl.

"It was a terrible mistake, and we knew it was wrong while we were doing it," Williams said after the league said between 22 and 27 defensive players were involved in the program he administered, with the knowledge of coach Sean Payton.

"Instead of getting caught up in it, I should have stopped it. I take full responsibility for my role," added Williams, now the defensive coordinator in St. Louis. "I am truly sorry. I have learned a hard lesson and I guarantee that I will never participate in or allow this kind of activity to happen again."

Williams, the Saints organization and the players involved face hefty fines and possible suspensions. The team could lose draft picks when NFL Commissioner Roger Goodell hands out punishment.

"It is our responsibility to protect player safety and the integrity of our game, and this type of conduct will not be tolerated," Goodell said. "We have made significant progress in changing the culture with respect to player safety and we are not going to relent. We have more work to do and we will do it."

The NFL said its findings were corroborated by multiple, independent sources. Asked about potential criminal charges, NFL spokesman Greg Aiello said:

"We believe that any violation of league rules should and will be handled by the commissioner."

All payouts for specific performances in a game, including interceptions or causing fumbles, are against NFL rules. The NFL also warns teams against such practices before each season.

Saints players contributed cash to the pool, at times large amounts, and in some cases the money pledged was directed against a specific person, the NFL said.

"The payments here are particularly troubling because they involved not just payments for ‘performance,’ but also for injuring opposing players," Goodell said in a statement. "The bounty rule promotes two key elements of NFL football: player safety and competitive integrity."

"Cart-offs" are defined by the NFL as a player being carried off the field; "knockouts" as when a player cannot return to the game.

The league absolved Saints owner Tom Benson of any blame, but said the investigation showed Payton and general manager Mickey Loomis knew about the "pay for performance" program.

"Although head coach Sean Payton was not a direct participant in the funding or administration of the program, he was aware of the allegations, did not make any detailed inquiry or otherwise seek to learn the facts, and failed to stop the bounty program. He never instructed his assistant coaches or players that a bounty program was improper and could not continue," the NFL said.

When informed about it earlier this year, the NFL said Benson directed Loomis to "ensure that any bounty program be discontinued immediately." However, the NFL’s report said evidence showed Loomis didn’t carry out Benson’s directions and that in 2010 Loomis denied any knowledge of a bounty program.

"There is no evidence that Mr. Loomis took any effective action to stop these practices," the NFL said.

The NFL found no evidence of similar bounty programs within the league, but several Redskins told The Washington Post that Williams had a similar system as defensive coordinator for the team.

Former defensive end Philip Daniels, now Washington’s director of player development, said he believed Williams paid off big hits with fines collected from players for being late to meetings or practices.

"Rather than pocket that money or whatever, he would redistribute it to players who had good games or good practices," said Daniels, who added the most he received was $1,500 for a four-sack game against Dallas in 2005.

"I think it is wrong the way they’re trying to paint (Williams)," Daniels told the Post. "He never told us to go out there and break a guy’s neck or break a guy’s leg. It was all in the context of good, hard football."

Benson responded to the NFL’s report saying: "I have been made aware of the NFL’s findings relative to the ‘Bounty Rule’ and how it relates to our club. I have offered, and the NFL has received, our full cooperation in their investigation. While the findings may be troubling, we look forward to putting this behind us and winning more championships in the future for our fans."

The NFL’s most infamous bounty case occurred in 1989 when Eagles coach Buddy Ryan was accused of putting a bounty on Cowboys players.

On Thanksgiving Day, Cowboys coach Jimmy Johnson accused Ryan of putting a bounty on Dallas quarterback Troy Aikman and placekicker Luis Zendejas before a 27-0 Philadelphia victory. Ryan and his players denied the charges and NFL Commissioner Paul Tagliabue found no evidence of wrongdoing.

The NFL began its Saints investigation in early 2010 after allegations surfaced that quarterbacks Warner of Arizona and Favre of Minnesota had been targeted. After interviewing several Saints who denied the bounty program existed and after the player who originally made the allegations recanted, the league couldn’t prove anything.

However, Goodell said the NFL "recently received significant and credible new information and the investigation was re-opened during the latter part of the 2011 season."

Warner, who retired after the 2009 season, responded to a fan’s comment on Twitter that even if the Saints had a bounty program a playoff hit on Warner was clean. Warner tweeted, "I would have to agree with you!!!"

"I don’t want to say that there was an attempt to injure, but I definitely think there were games where I could tell you that it seemed that they went beyond what was normal in regard to when they were going to hit me or how they were going to hit me," Warner said on the NFL Network. "Again, not with the intention necessarily of hurting me, but knocking me out of my game to get me to think about things differently. If by chance they hit me and knocked me out of the game, maybe that’s a benefit for them."

Favre’s agent, Bus Cook, said he was unaware of the investigation until Friday. He said the Saints should have been penalized for several hard, late hits during the 2009 NFC championship game and that he believed the contact was not coincidental.

"It was pretty obvious that the intent was to take Brett out of the game, and it happened the week before with Kurt Warner, too," Cook said. "I don’t know anything about whether it was by design or whatever, but I think a lot of people shared that same viewpoint that there were some hits that didn’t get called."

Cook, however, said Favre never suggested to him he was maliciously targeted.

"That’s part of football, getting hit," Cook said. "Brett never complained to me one way or another."

After the news broke Friday, tackle Joe Staley of the San Francisco 49er tweeted: "Just seeing all the reports about the Saints D. I knew there was something fishy about getting punched in the face during our playoff game"

The 49ers beat the Saints 36-32 in the NFC divisional playoffs.

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AP Sports Writers Janie McCauley in San Francisco and Dave Campbell in Minneapolis contributed to this story.