Neither the Football Association or local police received complaints after the incident which followed a 1-1 draw at Kenilworth in the FA Cup third round.
Carragher added: "I just reacted. People from Liverpool have got something about them and if they're not happy about something they let you know."
A Luton spokesman said the incident was being investigated by their safety officer, although could not confirm or deny it took place.
Liverpool will play Luton in their third-round replay at Anfield on Tuesday 15 January.