UEFA has opened disciplinary proceedings against Borussia Dortmund after stairwells were blocked ahead of the round-of-16 first leg clash with Tottenham Hotspur.
European football's governing body has charged BVB with a breach a safety and security regulations before the game, which Dortmund won 3-0.
The case will not be heard by UEFA's Control, Ethics and Disciplinary Body (CEDB) until May 19, however. BVB could face a fine or be forced to play a European match behind-closed-doors next season.
In a separate incident, there were also troubling scenes outside the ground and Tottenham fans were injured as they tried to enter the Westfalenstadion.
German police used pepper spray and batons on home and away fans, described by Tottenham as "completely unnecessary and unacceptable."
After the match, the authorities confirmed that 17 English fans suffered irritation to their eyes and a Dortmund police statement blamed supporters' late arrival at the stadium for "an exertion of pressure on the gates," which resulted in "some 80 supporters" entering the stadium "uncontrolled."
That prompted the authorities to temporarily close the gates and, after they were reopened, there were "conflicts between visiting fans and security," according to the police statement.
Spurs, though, said the police's "misdirection" of supporters was responsible for the situation.
"The misdirection of our fans by police along with the closing of turnstiles created a potentially dangerous situation," a Tottenham spokesperson said in a statement released to ESPN FC last week.
"We arranged for our fans to meet with officials of Borussia Dortmund immediately after the game. We have also spoken to officials at the club ourselves and they have taken on board our concerns."
The Tottenham Hotspur Supporters' Trust (THST) met with BVB club officials immediately after the match and disputed the police version of events.
The THST has asked supporters to send in accounts of what happened outside the stadium and plans to send a dossier to both clubs and UEFA's head of security.
"We are asking them to take the time to read and digest every single one of those accounts and take note of what people are saying because it's vastly important that their voices are heard and that this does not happen again," THST co-chair Katrina Law told ESPN FC.
"In terms of getting compensation for fans, that isn't going happen, but we need demonstrable evidence that BVB accept responsibility, that their stadium management accepts responsibility for the mistakes they made, that the police accept responsibility for what they did and stop this narrative of blaming the fans, which is frankly insulting, and that they put in place proper entry procedures at that stand.
"I would expect to go back there and make sure that's happened."
On Friday, Dortmund police said in a press release that the "overall situation at the gates, including the use of pepper spray from police, is part of a police investigation" and added that "the result of this investigation remains to be seen."
Tottenham face Dortmund at White Hart Lane on Thursday for the second leg.