The incident, at the Simple Digital Arena in Paisley on Tuesday night, left St Mirren goalkeeper Vaclav Hladky badly shaken and requiring attention from the club’s medical team.
The missile was thrown from the away end of the ground towards his goal and landed with a loud bang.
It is the latest in a series of dangerous incidents involving fans this season, which have also included coin throwing, pitch invasions and seats being thrown, as well as abusive singing from the terraces.
In response to the latest incident, Mr Yousaf tweeted: “Simply unacceptable scenes last night & over the weekend. When I speak to the Police they tell me it is a matter of when, not if, someone is seriously injured by a pyrotechnic.
“Will work with stakeholders to see if the law can be tightened in this area. Clubs must do more too.”
Strict liability has been suggested by some as a route to tackling the issue of fan behaviour at grounds, with proposals to either close stadiums fully or in part to supporters.
Speaking after the match, Celtic manager Neil Lennon condemned the individuals responsible for the latest incident.
“It serves no purpose in a football ground. I don’t see the motivation for anyone to bring a flashbang or pyrotechnic into a stadium,” he said.
“The health and safety of the players and officials is paramount. It didn’t just spook the St Mirren keeper, but some of our players too.
“Ryan [Christie] was also spooked and the goalie might have burst an ear drum. It delays the game when we have scored a goal and want to get going again. It serves no purpose whatsoever.
“The club have made a real stand in condemning it at times. I don’t understand why people want to do that. There is no logic in it.
“Why does an individual want to bring that to a game? It doesn’t impress anyone, it doesn’t add anything.
“It just damages people - and it could have damaged a player. It damages the reputation of the good fans we have and we just don’t want it.”
St Mirren manager Oran Kearney said he had considered taking his players off the pitch following the incident.
He said: “It is crazy to think we might have had to use an outfield player in goal.
“It is mad to think of how that possibly could have ended up. You are tempted to walk your team off the pitch.
“We are hopeful that thankfully it hasn’t ended up more sinister than it could have.
“I am standing 50 or 60 yards away and it made me jump. So if he [Hladky] is a yard [away] or however close, I dread to think the sound that came off.”