The Chicago Cubs have banned indefinitely from Wrigley Field the fan that used what appeared to be a racist hand gesture behind an African American television reporter during a game at their ballpark.

The Cubs sent a letter Wednesday to the bearded man who flashed the offensive sign in back of former Cubs outfielder Doug Glanville, who was working for NBC Sports Chicago on Tuesday night. The team said it had been unable to contact the fan by phone, and didn’t publicly identify him.

President of Business Operations Crane Kenney said the fan could be prosecuted for criminal trespass if he tries to enter the stadium.

“The individual responsible will not be welcome back at Wrigley Field,” Cubs spokesman Julian Green said.

Green said the man purchased his ticket on StubHub. Another fan reported his gesture to the team by text during the game against the Miami Marlins — by the time security arrived, the man was gone.

Glanville, who played three seasons for the Cubs, was standing beside the dugout discussing Chicago’s surging offense when the man seated in the background started gesturing.

Wearing a gray Cubs sweatshirt and blue pants, he made an upside-down “OK” sign near Glanville’s head during the broadcast. The gesture is associated with the juvenile “circle game,” where someone tries to trick a friend or sibling into looking at it, then punches them in the shoulder.

But the symbol has also become a white supremacy sign.

“It doesn’t matter either way,” Green said. “This was bad judgment on the part of the individual. Whether sophomoric behavior or some other stunt, to use that in connection with a respected journalist, who happens to be African American, and doing his job to deliver enjoyment to our fans is ignorant. It has no place @ Wrigley Field.”

Glanville said in a statement he was made aware of what the fan did after the segment. He praised the Cubs and NBC Sports for their “responsiveness.”

“They have reached out to me and are supportive of my role in the broadcast and continue to have a desire to uphold an inclusive environment at Wrigley Field,” he said. “They have displayed sensitivity as to how the implications of this would affect me as a person of color. I am supporting their efforts in fully investigating the matter and I will comment further once the investigation has run its course.”

NBC Sports Chicago senior vice president and general manager Kevin Cross called the fan’s behavior “reprehensible.”

Kenney earlier said “such ignorant and repulsive behavior is not tolerated” and “any individual behaving in this manner will not only be removed from the ballpark, but will be permanently banned from Wrigley Field.”

President of Baseball Operations Theo Epstein called the gesture “truly disgusting” and said it “gave me shivers to watch that.”

“We’ve made clear how egregious and unacceptable that behavior is and there’s no place for it in our society, in baseball and certainly no place at Wrigley Field,” he added.

The Cubs have been on a roll, surging into the NL Central lead, after a slow start. But they have also dealt with some difficult issues.

Infielder Addison Russell rejoined the team Wednesday after completing a 40-game suspension for violating Major League Baseball’s domestic violence policy and spending extra time in the minors to get ready.

Last month, MLB launched an investigation into racist messages sent to Cubs reliever Carl Edwards Jr. on Instagram. Those messages came from several people, agent Lee Long said at the time. Edwards got off to a rough start and was sent to Triple-A Iowa a month ago before getting recalled Monday.

The Cubs also distanced themselves from team patriarch Joe Ricketts in February because of emails written by him that included Islamophobic comments as well as conspiracies about former President Barack Obama’s birthplace and education.

“There is no extra incentive to be proactive and take action against racism and hate speech,” Green said. “When you see something wrong and offensive, you take swift action period.”

The Cubs certainly are not the only team that has had to deal with racial incidents.

The NHL’s Chicago Blackhawks banned four fans last season for directing racist taunts toward Washington Capitals forward Devante Smith-Pelly.

The Boston Red Sox banned a fan that used a racial slur to another fan about the performance of the national anthem as it was being sung by a woman from Kenya. That incident happened just days after Baltimore’s Adam Jones was subjected to racial taunts at Fenway Park.

MLB issued a statement Wednesday noting it has a policy that bans derogatory language and actions at its ballparks and requires clubs to have a response plans.

“Our inclusion efforts, policies and bullying prevention programming aim to make our sport and its ballparks welcome to all, and we will do everything possible to accomplish that goal,” MLB said.