UEFA has blamed "fake tickets" for the chaos that occurred outside the Stade de France ahead of the Champions League final on Saturday night.
Liverpool supporters were caught up in huge crowds as they tried to get into the ground in time for the 8pm kick-off against Real Madrid, with the match being delayed by 36 minutes.
Fans were tear-gassed by police as things spiralled out of control while pop star Camila Cabello serenaded the supporters inside the stadium.
Liverpool have demanded a "formal investigation" into what happened, with UEFA releasing a statement reading: "In the lead-up to the game, the turnstiles at the Liverpool end became blocked by thousands of fans who had purchased fake tickets which did not work in the turnstiles.
"This created a build-up of fans trying to get in. As a result, the kick-off was delayed by 35 minutes to allow as many fans as possible with genuine tickets to gain access.
"As numbers outside the stadium continued to build up after kick-off, the police dispersed them with tear gas and forced them away from the stadium.
"UEFA is sympathetic to those affected by these events and will further review these matters urgently together with the French police and authorities, and with the French Football Federation."
Liverpool's statement read: "We are hugely disappointed at the stadium entry issues and breakdown of the security perimeter that Liverpool fans faced this evening at Stade de France.
"This is the greatest match in European football and supporters should not have to experience the scenes we have witnessed tonight. We have officially requested a formal investigation into the causes of these unacceptable issues."
Real won the final 1-0 thanks to a second-half goal from Vinicius Junior, dashing Liverpool's hope of a seventh European crown.
Liverpool defender Joel Matip's brother Marvin was caught up in the drama with his pregnant wife ahead of the final and had to flee for safety inside a restaurant.
Marvin told Sky Sport: "The organisation around and in the stadium is unworthy of a Champions League final! Using tear gas in areas with children and uninvolved fans is dangerous."
BT Sport trio Michael Owen, Rio Ferdinand and Steven Gerrard also commented on the chaos ahead of the fixture.
"It is so sad and obviously everything has to be military precision out there," said Owen. "We don't know what's gone on, but it is sad to hear. You just hope everyone is safe."
Ferdinand added: "We pray for people's safety. You come to football to be entertained." And Gerrard said: "You just hope there are no issues out there and everyone gets home safely."
Alan Shearer, meanwhile, said on BBC 5 Live: "We have to hope that everyone outside is OK. For the players, their preparation is meticulous to the minute. They have warmed up and their day has been designed for kick-off at a certain time."
BBC Journalist Nick Parrott was outside the ground in a personal capacity and found himself caught up in the chaos. He told BBC Radio 5 Live: "I have just been pepper-sprayed for the first time in my life. I have been to the Champions League final before and I have never been pepper-sprayed before.
"I was outside Gate Y which has been opening and closing repeatedly over the last hour and a half but nobody has been going through. The security staff on the other side advanced and sprayed pepper spray.
"I have seen 10 fans trying to climb over fences. Gate Z is open but there does not seem to be any movement going in. I have never seen this sort of chaos at any match I have been to in a personal capacity.
"The Liverpool fans are trying to move themselves back from these gates to try and get in but the authorities seem to be doing nothing. I came to get into the stadium at seven o'clock.
"I got through the outer perimeter where there is crushing. I came round in good time and it was quite clear that we were not going to get in before nine o'clock."
