Posts targeting migrants remained online during riots despite 5pm plea from online safety tsar
Niamh Hodnett was appointed last year to fight harmful content online.
Niamh Hodnett contacted major social media firms on evening of 23 November to warn about potential for violence.
Posts calling for migrants to be "killed" were shared on social platforms as riots unfolded.
Immigrant Council of Ireland warned about the proliferation of such posts and called for posters to be investigated.