An Ulster Rugby spectator has been handed a lifetime ban by the club over abuse directed at Simon Zebo.
It happened during a European fixture against Racing 92 at the Kingspan Stadium.
In a statement, Ulster thanked supporters who came forward with information on the incident after CCTV footage proved inconclusive.
Following the match, Zebo sent a tweet which was widely interpreted as saying the abuse was racist.
It is understood that the man who has been banned is not a registered Ulster Rugby season ticket holder.
On Tuesday, an Ulster Rugby spokesperson said: "Following a robust investigation into allegations of abuse directed at Simon Zebo during the fixture versus Racing 92, Ulster Rugby has sanctioned a lifetime ban on a spectator, for breaching our stadium regulations.
"We are all very proud of our reputation as an inclusive club and the unacceptable behaviour of this one individual is not reflective of our supporters, or the values of our club.
"We have issued a written apology to Simon Zebo and Racing 92."
On Tuesday Ireland international Zebo thanked Ulster for their response.
Following the Champions Cup clash on 12 January, Zebo had tweeted: "I hope my ears deceived me with some comments directed my way from the crowd. #Not on - Django wins in the end."
It referenced Quentin Tarantino's 2012 film Django Unchained about an African-American slave.
Zebo's father is from the Caribbean island of Martinique, while his mother is Irish.
In a statement issued to season ticket holders on Tuesday, Ulster Rugby CEO Johnny Petrie said: "We will be putting additional measures in place to ensure that we have a safe, positive atmosphere at the stadium and supporters are encouraged to immediately report any future incidents to a steward.
"This extends to the broader game in Ulster as well - rugby should be fun to watch from the touchlines, and we will not tolerate any forms of abuse; be it from supporters, parents or coaches."
Speaking to Jim Hamilton from Rugby Pass, Zebo said he had expected a "rough time from the crowd", but that most it was "good-natured".
In October the former Munster player, who moved to French club Racing 92 at the beginning of the season, apologised to Ulster full-back Michael Lowry for his celebration of a try in the reverse fixture in Paris.
Zebo pointed his finger towards the 20-year-old before diving over at the end of his side's 44-12 victory in Paris.
It prompted referee Nigel Owens to tell the former Munster full-back to apologise to Lowry, which he did on the pitch and in a tweet after the game.
In his interview with Rugby Pass following the incident in Belfast, Zebo said: "It was something that happened to me quite a bit when I was younger, you know you're dealing with other kids or children or teenagers, who don't have the intellect or education at the time to understand how things like that can hurt a person.
"So it was even more disappointing that I went home and it was an elderly man, 40-plus, so that's why it just annoyed me a bit.
"But it is water off a duck's back now for me, I'd be quite bullet-proof in terms of that."
In the interview, Zebo praised the response from Ulster Rugby in the aftermath of the match, adding that he had received messages of support for a number of players.