The Green Brigade Celtic 'ultras' group has accused the person who threw a firecracker on to St Mirren's pitch of inflicting harm on their fellow fans.
Police and Celtic are investigating after St Mirren goalkeeper Vaclav Hladky needed treatment after the loud bang unsettled him and several Celtic players, with the firework landing yards from his goal during a 2-0 win for the Ladbrokes Premiership leaders on Wednesday.
St Mirren manager Oran Kearney was "tempted" to lead his players off the pitch and Celtic boss Neil Lennon was baffled at why the perpetrator had done something that damaged the club's reputation.
The incident followed an encroachment on to the sidelines by a small group of Celtic fans – including a man carrying a toddler – when Odsonne Edouard scored the opener against Rangers on Sunday. A steward needed treatment after being hurt in the ensuing crush.
Pyrotechnics are banned by law in Scottish football grounds but smoke bombs in particular are a regular feature at games.
The Green Brigade has been associated with their use but distanced itself from the latest incident.
In a statement posted on social media, the Green Brigade accused the Scottish Government, police and judicial system of seeking to build support for "another assault on the rights of football supporters" following the repeal of the Offensive Behaviour at Football Act.
The statement added: "Over the last few months these figures have cynically sought to feed a sense of moral panic around football, casting fans as villains for their own gain.
"The mainstream media have fuelled this fire with sensationalist headlines, disproportionate coverage and click-bait journalism.
"With this in mind, it is imperative that the victory against the OBFA does not become hollow and it is clear that all fans share the responsibility to counter any attempts to replace it – which includes being responsible for your own actions and behaviour.
"While there must be a sense of perspective regarding the recent media furore, fans must realise the potential trouble they are inflicting on themselves and other fans by feeding this frenzy.
"As an ultras group, we support the safe, sensible use of pyrotechnics, however the launching of pyrotechnics on to the park or in the direction of people is both unnecessary and counterproductive to any aspirations of normalising its use.
"Similarly, small-scale pitch invasions – whilst largely harmless – are simply giving our detractors further ammunition.
"We take particular exception to anyone who uses our name, banner or numbers as cover to indulge in behaviour which will ultimately cause our group and the Celtic support harm."
Celtic vowed to take "the strongest action possible" if they are able to identify anyone involved in the incident.
Chief executive Peter Lawwell said: "Last night's incident was completely unacceptable and not something we ever want to see repeated. The safety of everyone in football – players, fans, staff, and officials – should always be our priority and, collectively, we need to do all we can to ensure this remains the case.
"There have a been a number of incidents across many clubs this season, with a range of items, including pyrotechnics, being thrown on to pitches. We need to do all we can to remove this from our game.
"From a Celtic perspective, the club does not want it, our players do not want it, our manager does not want it and our supporters do not want it.
"There are serious safety concerns associated with such behaviour, and regardless of the obvious reputational damage which this kind of behaviour has on the club, there are numerous potential repercussions which could have hugely detrimental consequences for the club and our supporters."
Scottish Justice Secretary Humza Yousaf vowed to look into new legislation after Wednesday's incident and tweeted: "When I speak to the Police they tell me it is a matter of when, not if, someone is seriously injured by a pyrotechnic."
