According to Catholicism, does God actively cause suffering in Hell? I was wondering what is the official ontological explanation of the Catholic Church in regard to human souls and fallen angles suffering in Hell. I do not know whether God actively punishes them with His absence or whether it's something else entirely.
Does the suffering in Hell come from not being able to bear God's presence? Or is Hell itself absence of God's presence? I don't know, though the first conclusion seems more logical to me, as God is omnipresent. Furthermore, God is Love, so I think that the suffering that comes from the free decision to turn away from Him is more plausible than God actively punishing sinners in Hell. After all, he is the just Judge, not a tormentor.
I hope that this speculation of mine is not heresy by Catholic standards. Thank you for your answers in advance.
Souls who die in mortal sin are actively punished, but others (e.g., those in the limbo for children, who died with original sin and no actual sin) are only passively punished (because deprived from the Beatific Vision).

St. Augustine writes (Enchir. xciii):


  The punishment of children who die in none but original sin is most lenient.