Police were called to reports of passengers causing disruption on a flight from Rome ahead of Albion’s Europa League clash.
The Ryanair flight arrived from the Italian capital at around 10.50pm on Wednesday evening, the night before Brighton played their second leg against Roma at the Amex Stadium.
Essex Police attended Stansted Airport but said no arrests were made. The force confirmed they are investigating the incident.
A spokesman said: “We were called to reports of public order offences and a sexual offence on a flight into Stansted Airport at about 10.50pm on Wednesday, March 13.
“We have opened an investigation and our enquiries are ongoing.”
Italian news site La Gazzetta dello Sport reported that five or six Roma fans on the flight were met by police at the airport.
Brighton beat AS Roma 1-0 but could not overturn the 4-0 deficit from the first leg to reach the quarter finals of the competition.
One person was arrested inside the stadium on suspicion of assault.
Sussex Police said: "We worked with partners including UEFA, Brighton and Hove Albion Football Club, Southern Rail and British Transport Police to manage the safe arrival and departure of supporters from the Amex Stadium.
"We’d like to thank the vast majority of both home and away fans who behaved responsibly before, during and after the game against AS Roma.
"Working with the club and emergency services colleagues, our aim was to ensure the evening was as safe and enjoyable as possible for everyone attending and to minimise disruption."
Hundreds of Roma fans took to the streets with flares and made their presence felt as they headed towards the Amex prior to the game.
It came a week after two Albion fans were stabbed in Rome ahead of the away leg of the tie.
A Ryanair spokesman said: “The crew of this flight from Rome to London called ahead for police assistance after a small group of passengers became disruptive onboard.
"The aircraft was met by local police upon arrival at London Stansted and these passengers were removed. This is now a matter for local police.”
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