J-League Chairman Mitsuru Murai profusely apologized on Friday for the appearance of a Gamba Osaka supporter's banner resembling a Nazi Schutzstaffel (SS) symbol at last weekend's derby match against Cerezo Osaka.

Murai said the league will decide what action to take against Gamba once the club complete their investigation. Gamba have already issued a blanket ban on flags and banners by their fans at all home and away games.

"We are deeply sorry for making everyone who supports the J-League and those overseas uncomfortable," Murai said, speaking at Todoroki Stadium following a 2-2 draw between Kawasaki Frontale and Shimizu S-Pulse. "I was told about the case last night and personally heard from the club president today to confirm what went on."

"It's a very difficult matter, but the Gamba president feels they clearly have to do more in terms of prevention and so do I. We know which supporter group is responsible for this, but we are still trying to identify the individual who put the flag up."

"We need to find out where this person is coming from and what kind of conversations he has been having. It makes a difference if he had no ill will or if he knew what he was doing."

"Once we find out all the facts, then we will take the next step. But as of right now, we believe there was no political motive behind this. Yet as we have previously said, this cannot happen."

This is the second time Murai has had to deal with a controversial banner raised by J-League fans.

In 2014, Urawa Reds supporters hoisted a banner at Saitama Stadium that said, "Japanese Only." The league came down hard on Urawa, forcing them to play one game at an empty ground.

Whether the league will act against Gamba remains to be seen, yet Murai said increased prevention measures will have to be taken in light of the latest case.

"When I became chairman in 2014, the "Japanese Only" incident occurred," he said. "At the time, we went over as a league how we have to deal with not only racism or discrimination, but also political issues among other things."

"Many people around the world feel sad about it. As we approach 2020, more and more foreigners will come to Japan. I think the football community needs to lead the way as an agent of change; saying you didn't know or that it was a fashion statement is not good enough. The commitment we made in 2014 was to eradicate such thinking but we clearly have to go back to the drawing board."

"We're not monitoring everything that happens on SNS but evidently, we do need to be more in tune. We have to review what we do and how we do it."

Earlier Friday, Gamba officials met with members of the group that displayed the banner to hear their side, but has banned the group from the team's games.

Speaking at Suita Stadium in Osaka, team president Takashi Yamauchi said, "This created an uncomfortable environment for those who love soccer and I apologize deeply for this."

"They said they did not intend to make a political statement but rather used that design to present a strong image."

In a statement posted earlier on their website, Gamba said: "The club, as well as of course the J-League, will not under any circumstances allow flags and the like bearing political or religious slogans. It is deplorable."

"In order to make sure this kind of thing never happens again, the club and management are not going to take half measures."