Millwall have pledged to identify the hooligans who ripped out seats at Hull City's KC Stadium at the weekend.
Hull are seeking financial compensation from the London club after more than 50 seats were ripped out and used as missiles at the stadium, and toilets were destroyed. Twelve people were arrested by police.
Andy Ambler, the Lions managing director, admitted his club and others still had a long way to go to eradicate the "element" that turn up just to cause trouble.
He told Sky Sports News: "No one has worked harder than Millwall to solve this problem but we need to realise that this problem is still there.
"I don't think we're going back to the old days, but there were other incidents over the weekend unfortunately and we have to continue to work hard.
"Every club has this element, and it is an element we need to eradicate from the game because it's damaging our national sport.
"We are not sure that (those involved) are Millwall fans. The majority of our fans are as upset about this as we are.
"We have a membership scheme which we are going to have to look at again because we sold nearly 3,000 tickets to members and season ticket holders and clearly some of these tickets got into the hands of these people who don't normally come to Millwall games."
The Football Association have called for the "strongest possible sanction" against the perpetrators.
"These are the sorts of things we never want to see in a football stadium," an FA spokesman said.
"We are working with the clubs and the police to investigate what happened."
Humberside Police are conducting an investigation into the events and are confident of catching the troublemakers.
Chief inspector Darren Downs told BBC Radio Five Live: "We have got CCTV evidence inside, we have got evidence gathering teams inside, there are photographs from press photographers.
"To be honest we know an awful lot of them already. We know the names, we know the faces because they have been involved in smaller level stuff and they have been trouble-causers for a while.
"I feel confident that virtually everyone involved in the disorder on Saturday will, at some point in the next few months, be brought to justice."
Hull chairman Paul Duffen, who confirmed his club would be seeking compensation from Millwall as a "private matter" between the clubs, added: "It's a difficulty in football generally to know exactly who you're selling tickets to.
"Certainly the people who caused this trouble were not Millwall fans, they were mindless hooligans who came under the guise of Millwall fans."
He also defended his club's segregation policy, adding on Sky Sports News: "There was no problem with segregation when the stadium opened, the difficulty was that because this group of people came with single intention of undermining the security in the stadium the first thing they did was tear up the segregation netting and we had to put a human barrier of stewards in place instead.
"The segregation we had on Saturday was absolutely adequate for hundreds of other games."