Police are investigating the December incident that took place between Pittsburgh Steelers wide receiver DK Metcalf and a Detroit Lions fan that ended in an altercation between the two. Per the Detroit Free Press’ Christian Romo, the Detroit Police Department is taking a closer look at the case.

“The Wayne County Prosecutor’s Office also confirmed to the Free Press that Detroit police submitted a warrant request on Jan. 21 that is currently being reviewed. Neither department revealed who the warrant request was for, while the prosecutor says that no one has been charged in relation to the incident.”

As the paper notes, it’s unclear what the warrant is in reference to and if it could potentially be against Metcalf. During the incident, Metcalf walked over to the front row of the stands and briefly exchanged words with the fan, Ryan Kennedy. Metcalf then reached up and grabbed at Kennedy, making contact before walking away.

The Press adds that a Detroit police spokesperson noted police have been “investigating.” It’s not clear when the investigation began.

The NFL suspended Metcalf from the final two regular season games for violating the league’s personal conduct policy that prohibits players from interacting with fans in such a manner. He lost on appeal, and Metcalf returned for the Steelers’ Wild Card loss to the Houston Texans. Traded from Seattle last March, he caught 59 passes for 850 yards and six touchdowns in his first year with Pittsburgh.

Earlier this week, Kennedy sued Metcalf, the Pittsburgh Steelers, Chad Johnson and other entities for $100 million with a main accusation of defamation. Johnson went on his podcast and said Metcalf allegedly told him Kennedy used the N-word toward Metcalf, resulting in Metcalf’s outburst. Publicly, Metcalf declined all comment about the altercation. A status conference for the civil suit is set for May 5.

Now, it appears there is a criminal investigation to determine if charges are warranted. It’s unclear when a decision could be made.

The Steelers won’t begin their offseason program until April 6.