(CNN) -- There's no evidence that anyone at the NFL saw or possessed a video showing Ray Rice punching his then-fiancée until it was made public, but the league should have known it needed to dig deeper into the incident, an external investigative report released Thursday concludes.
The report wraps up an inquiry by former FBI Director Robert Mueller into how the NFL initially investigated the then-Baltimore Ravens running back's attack on Janay Palmer last February at the Revel hotel and casino in Atlantic City.
"We concluded there was substantial information about the incident -- even without the in-elevator video -- indicating the need for a more thorough investigation," Mueller said in his report. "The NFL should have done more with the information it had, and should have taken additional steps to obtain all available information about the February 15 incident."
The NFL asked for Mueller's report in September after a public outcry over the NFL's initial handling of the incident.
The league at first suspended Rice for two games, based on an initial video from outside an elevator that only showed Rice dragging Palmer out. Later, additional footage that showed Rice punch Palmer -- then his fiancée but now his wife -- prompted NFL Commissioner Roger Goodell to suspend the player indefinitely.