A 15-year-old boy has been arrested after Luton Town player Peter Kioso was racially abused online, police have said.
The comments were understood to have been made on an Instagram live stream, according to Cleveland Police.
Kioso, who had made his club and league debut last week, was broadcasting on the social media app after his team defeated Blackburn Rovers to avoid relegation from the Championship on Wednesday.
The 21-year-old Irishman later posted on Twitter to show the abuse he had received.
"This happened on Wednesday night after the boys and I were celebrating such a big thing that we did and I was not going to let that ruin the moment, but now that everything has calmed down I feel like I shed light on it to let everyone know how things still are in 2020," he said.
Police have said the teenage boy from the Hartlepool area was arrested on Friday evening on suspicion of a racially aggravated public order offence, but he has since been released while investigations continue.
In a statement, Kioso's club added: "All at Luton Town are appalled that discriminatory comments can be directed towards anyone in this day and age, but we are especially upset for one of our young players, Peter Kioso, who has been subject to shameful abuse this week.
"As a club and a town which celebrates equality, diversity and inclusion, we firmly stand behind Peter and all of our minority players and staff regardless of their skin tone, ethnicity or religion.
"We have been helping the police with enquiries to bring the perpetrator of this mindless act to account."
Anyone with information regarding the comments is asked to contact Sergeant Adrian Dack, from the football intelligence unit at Cleveland Police, on 101