New York: An independent investigation led by former FBI director Robert Mueller will look into the NFL’s handling of the Ray Rice domestic violence incident, NFL commissioner Roger Goodell said on Wednesday night.

The probe, which will conclude with a public report, will have the full cooperation of the league in obtaining records and interviews with league staff members.

The move came as pressure mounted on Goodell regarding exactly when the league first saw and obtained a video showing star Baltimore Ravens running back Rice knocking out his then-fiancee and now-wife, Janay Palmer, in a hotel elevator.

The probe will be overseen by two NFL team owners who are attorneys, Art Rooney of the Pittsburgh Steelers and John Mara of the New York Giants, and conducted by Mueller, who ran the FBI from 2001 to 2013.

Mueller’s investigation will look into how the NFL handled its initial probe of Rice, which Goodell said did not produce the key video despite requests to law-enforcement officials, in part because it would have been illegal interference in an ongoing legal matter.

Rice avoided jail time for the incident by agreeing in May to a pre-trial intervention programme. In July, Goodell, who has guided the NFL since 2006, imposed only a two-game ban on Rice, one that was to have ended Friday.

Last month, Goodell said that he had given too soft a punishment, and toughened NFL penalties for domestic violence.

Only after video of Rice’s brutal left hook was revealed on Monday by celebrity website TMZ did the Baltimore Ravens fire Rice, a star rusher who helped them win the 2013 Super Bowl, and Goodell suspend Rice indefinitely.

Lawmakers step in

US lawmakers who oversee the NFL and its anti-trust exemptions regarding television deals criticised Goodell and requested details on the NFL’s investigation of Rice.

US Senator Dean Heller, a Republican on a Senate Commerce subcommittee with jurisdiction over the NFL, pressed for details about how Goodell will “address the harm your league has inflicted on survivors of domestic violence going forward.”

“Commissioner Goodell must understand the scope and severity of domestic abuse acts,” Heller wrote. “Judging from his actions, it’s time for the NFL to step its game up on this important matter.

“I am highly disappointed the NFL’s reaction was only heightened once the public witnessed the elevator video. By waiting to act until it was made public, you effectively condoned the action of the perpetrator himself.”

And the leader of America’s largest women’s advocacy group called for Goodell, the boss of the world’s richest sports league, to resign.

“The NFL has lost its way,” said National Organisation for Women president Terry O’Neill. “It doesn’t have a Ray Rice problem. It has a violence against women problem.

“The only workable solution is for Roger Goodell to resign.”

Goodell maintained no one at the NFL had seen the brutal video of Rice punching Palmer in an Atlantic City casino elevator last February before Monday.