Washington, DC (SportsNetwork.com) - Former FBI director Robert Mueller said his investigation found no evidence that the NFL saw the elevator video of Ray Rice striking his then-fiancee before the tape was released in September.

Mueller's report did, however, say the league should have conducted a more thorough investigation of the incident before issuing the initial two-game suspension to Rice, who was then suspended indefinitely after the video inside the elevator showed the former Baltimore Ravens running back punching Janay Palmer and knocking her unconscious.

Rice, who was released by the Ravens after the additional video came to light and just before the league announced its extended suspension, won an appeal of the extensive penalty but did not play during the 2014 season.

NFL commissioner Roger Goodell was widely criticized for his handling of the case, which stemmed from Rice's assault of Palmer -- now his wife -- in the elevator of an Atlantic City casino in February.

Goodell said the league never saw the video of the actual punch until it was released by TMZ.com in September, but a report from the Associated Press said a law enforcement official said he sent a copy of the video to an NFL executive in April, two months after the incident and five months before the initial suspension was issued.

The AP story said a woman at the NFL's office confirmed receipt of the video in an April 9 phone call, prompting the league to give Mueller authority to conduct an independent investigation.

According to Mueller's report, he and his colleagues interviewed more than 200 NFL employees and contractors, including "every female employee, contractor or vendor whose electronic badge recorded that she was in the league's main office on that day."

Digital forensics experts searched computers and mobile phones of the league's senior executives, including Goodell, for any evidence of the in-elevator video.

Investigators also reviewed "millions of documents, e-mails, text messages and electronic data logs" during the four-month inquiry.

In summarizing the process, Mueller concluded: "We found no evidence that anyone at the NFL had or saw the in-elevator video before it was publicly shown. We also found no evidence that a woman at the NFL acknowledged receipt of that video in a voicemail message on April 9, 2014.

"We concluded there was substantial information about the incident -- even without the in-elevator video -- indicating the need for a more thorough investigation. The NFL should have done more with the information it had, and should have taken additional steps to obtain all available information about the Feb. 15 incident."

Mueller's report said the NFL has done well to change its personal conduct policy in the wake the incident, but added that the league needs to be more assertive in its investigations and rely less on the legal system.

"The investigators identified a "weakness" -- as they call it -- in the league's long-standing practice of deferring to the criminal justice system when matters like this arise," said New York Giants president John Mara and Pittsburgh Steelers president Art Rooney II in a statement after Mueller's report was issued. "Mr. Mueller concludes that the league should have conducted a more substantial independent investigation of this matter and he has made six recommendations. This morning, we spoke to commissioner Goodell about these recommendations. We want to review them and understand them in greater detail. We look forward to moving forward on this."

Goodell's credibility came under scrutiny during the process, but the owners' statement following Mueller's report backed the commissioner's actions.

"It is clear to us that commissioner Goodell was forthright in the statements he made to the owners about this matter, and we have every confidence that Roger Goodell is the right person to lead the league as we move forward," Mara and Rooney said.

The Rice case spurred the NFL into stronger penalties for domestic violence.