Both Liverpool and the Merseyside Police have been made aware of the chaos outside Benfica's Estadio da Luz on Tuesday night that left thousands stuck outside the ground.
It's estimated that thousands of supporters in Lisbon were forced to miss part of the Reds' 3-1 win because of the poorly organised system of entry before the Champions League quarter-final first leg.
Several supporters in Portugal have told the ECHO about what they felt was a heavy-handed and "antagonistic" police presence who appeared ready for hostility from match-goers.
READ MORE: What Liverpool fans sang after Luis Diaz goal says a lot about Jurgen Klopp
PLAYER RATINGS: Naby Keita brilliant and Trent great against Benfica
Those looking to get into the stadium on Tuesday were corralled into a tight area outside the ground before they were slowly allowed to enter in single file after a rigorous search because of a lack of working turnstiles.
It is understood that large queues began to form around an hour before kick-off as Liverpool fans looked to take their seat for the quarter-final clash against the Portuguese giants. However, most Reds fans were not permitted entry until all the home crowd had filtered into the ground, leaving thousands of seats empty in the away end as the match got underway.
Supporters have spoken of the overly invasive, aggressive and officious searches that some felt were designed to frustrate the crowd into hostile reactions to a police unit in riot gear.
The ECHO understands that supporters' union, the Spirit of Shankly, have spoken to both the Merseyside Police and Liverpool FC.
Liverpool fans have also been praised by those who were affected for their calmness throughout a situation that some believe could easily have turned violent had frustrations boiled over. After the game, Reds followers were kept behind for an hour on the concourse of the ground before being marched to the nearest tram station by police.
"The way we’ve been treated in Lisbon tonight is dangerous and a disgrace," tweeted one fan, while another added: "They were antagonising the crowd to create trouble. [We had] absolutely no issues with the Benfica fans all day."
Football journalist Simon Hughes was at the game and was caught up in the chaos as a result. The Athletic reporter tweeted on Wednesday: "Still angry, frustrated and relieved about last night. Not the match. The before and after. Limited stewarding. Lots of police. No obvious plan on entry. No signposting. Then an unnecessary frogmarch to the metro. They weren’t dealing with ultras. Lots of old men, women and kids. Everything [was] so unnecessary."
On Wednesday, Football Supporters Europe (FSE) confirmed they were liaising with UEFA over the incident as Liverpool and MerPol discuss what can be done to avoid such situations going forward.
They tweeted: "Access to last night’s game was a shambles and there were also health and safety concerns within the away end. We have already made representations to Liverpool FC and Merseyside Police along with reporting these issues to FSE who have direct access to UEFA. If you were at the game last night please complete the survey #fansdeservebetter."
On the pitch itself, Jurgen Klopp's men took a giant stride towards a third Champions League semi-final in four years thanks to goals from Ibrahima Konate, Sadio Mane and Luis Diaz, despite a strike from Darwin Nunez for the home side shortly after the restart.
If Liverpool navigate the second leg at Anfield next week without any problems they will meet either Bayern Munich or Villarreal for a place in the Paris final on Saturday May 28.
