(CNN)The horse racing industry is facing renewed scrutiny over animal welfare after footage emerged showing an amateur jockey jumping onto the back of a dead horse.
On Tuesday, the Irish Horseracing Regulatory Board tweeted that it was "aware of further social media content circulating and the matter is under investigation."
The video, which was widely circulated on social media on Monday, shows people laughing and joking when an individual poses on the back of the stricken horse. The group appears to be standing on the gallops, where racehorses train.
The man who sits on the horse is yet to be officially confirmed by authorities but, in an interview with The Irish Field, amateur jockey Rob James confirmed it was him and apologized for his actions.
"To try defending my stupidity at the time would add further insult and hurt to the many loyal people that have supported me during my career," he said, stating the video was taken nearly five years ago.
"I have caused embarrassment to my employers, my family and most importantly the sport I love.
"I am heartbroken by the damage I have caused and will do my best to try and make amends to those hurt by my conduct."