NFL commissioner Roger Goodell has appointed former FBI Director Robert S. Mueller to conduct an independent investigation into the NFL's pursuit and handling of evidence in the Ray Rice domestic violence incident.

The announcement was made late Wednesday night, just hours after the Associated Press reported that a law enforcement sent a DVD to an NFL executive five months ago that showed video of Rice punching his then-fiancee in the face during an argument in an Atlantic City casino elevator.

Mueller's investigation will be overseen by NFL owners John Mara of the Giants and Art Rooney of the Steelers, both of whom are attorneys. The report will be made public when it is completed. Goodell pledged that Mueller, who served as director of the FBI from 2001-13, will have the full cooperation of NFL personnel and access to all NFL records. Mueller is currently a partner in the law firm of WilmerHale and is based in Washington.

Goodell has insisted that no one from the NFL's office had seen video of the punch until it was distributed by the website TMZ on Monday -- images that quickly resulted in Rice being released by the Baltimore Ravens and the NFL suspending the running back indefinitely.

The source played for the AP a 12-second voice mail left from an NFL office number on April 9 that confirmed the video had been received. A female voice can be heard expressing thanks and saying, "You're right. It's terrible."

NFL spokesman Brian McCarthy said Wednesday night: "We have no knowledge of this. We are not aware of anyone in our office who possessed or saw the video before it was made public on Monday. We will look into it."

Goodell and the league have faced severe public criticism for how they handled Rice's domestic violence case. Goodell initially suspended him for two games before the video became public.

AP said the law enforcement official, who spoke on condition of anonymity, had no further communication with anyone from the league and could not confirm whether anyone watched the video. He asked the AP not to release the name of the NFL executive with whom he communicated lest it reveal the official's identity as the source.

The league has said it asked for but could not obtain the video, which showed Rice punching Janay Palmer, whom he later married, and rendering her unconscious.

In an interview with CBS News on Tuesday, Goodell reasserted that no one in the NFL had seen that video, but after a pause, he added "to my knowledge."

"We assumed that there was a video," Goodell told CBS. "We asked for video. But we were never granted that opportunity."