Mob Spawner(specifically blaze as far as I'm aware) will emit particles and also continue to create mobs after being destroyed. Placing a block in the same spot has no effect. Placing another spawner in the same place w/ another mob seems to work normally, but the blazes will keep spawning. As far as I could tell, they will keep multiplying as well, until you set the gamemode to peaceful.
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Asteraoth
Thank you for your report!
However, this issue is a Duplicate of MC-137463.
If you have additional information, please add it to that report.
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