Pompey have threatened to ban any fan found in possession of a flare or smoke canister.
At Dagenham & Redbridge last weekend, two blue smoke canisters were released onto the pitch in the second-half from the away section.
The first arrived following Michael Doyle’s 59th minute leveller, delaying resumption of the game while stewards removed it.
Pompey have already been reported to the Football Association over a number of incidents involving explosive devices.
The offence also carries a possible prison sentence and a three-year football banning order as a minimum.
The Blues have also warned supporters found in possession of a flare, firework or smoke canister in or around a football stadium will be banned from Fratton Park indefinitely and face criminal charges.
And manager Paul Cook has reinforced the message.
Cook said: ‘When I saw the smoke in the goalmouth after the goal, the team and I were annoyed and frustrated.
‘We had just put Dagenham on the ropes and we wanted us to get back into them as soon as possible.
‘Instead vital momentum was potentially lost and it could have cost us a vital three points. It has to stop, and stop now.’
Trust chairman Ashley Brown added: ‘Thankfully we managed to get the win in the end on Saturday and no-one was hurt, but if this sort of behaviour continues the club will be subject to heavy fines or potentially even receive supporter or points related sanctions.
‘The people who throw these, or in fact anything else at matches, are causing significant damage to the club they claim to support.’
Chief executive Mark Catlin said: ‘Our security team liaise constantly with other clubs and the police. Other Pompey fans have already been in touch with the club providing information on this incident.
‘The fans who did this will be caught, of that I am in no doubt, and when they are they will be banned. The club will also support a criminal prosecution of those identified.’