The NFL has launched an investigation into the Oakland Raiders' head coach hiring process and whether they violated the Rooney Rule, a league official told ESPN's Adam Schefter.

The investigation comes one day after the Fritz Pollard Alliance called on the NFL to investigate whether the rule on minority interviews was violated by the Raiders when they hired Jon Gruden as coach.

Fritz Pollard Alliance counsel Cyrus Mehri and N. Jeremi Duru issued a statement Wednesday expressing concern that Raiders owner Mark Davis came to an agreement with Gruden before the team interviewed any minority candidates.

The NFL has issued discipline for Rooney Rule violations in the past. Then-Detroit Lions general manager Matt Millen was fined $200,000 for circumventing the rule when he hired Steve Mariucci as the team's head coach in 2003.

Davis said Tuesday after introducing Gruden as the team's new coach that he believed Gruden was "all-in" to take the job during a meeting on Christmas Eve. Davis fired Jack Del Rio a week later, and the team officially hired Gruden on Jan. 6.

Raiders general manager Reggie McKenzie said Tuesday he interviewed two minority candidates before Gruden's hiring was announced. Those candidates were Oakland tight ends coach Bobby Johnson and USC offensive coordinator Tee Martin.

The Rooney Rule requires teams to interview at least one minority candidate as part of an open process.

The Fritz Pollard Alliance is dedicated to promoting diversity and equality of job opportunity in the coaching, front-office and scouting staffs of NFL teams.

ESPN's Kevin Seifert and The Associated Press contributed to this report.