Hagrid in Azkaban

[Amy Z]

No: HPFGUIDX 18572

Help!  A tip-of-the-tongue memory is driving me crazy.  I know I read 
a sentence just the other day saying that Hagrid had been in Azkaban 
twice.  I'm all-but-certain it's from one of the books (3 or 4, of 
course).  Two questions:

(1) Can you direct me to the source?  *Was* it in the books?

and (2) Is this a Flint, or is it a clue, or did Hagrid really get 
sent to Azkaban when he was expelled?  If so, how was he 
released--purely through Dumbledore's influence?

Amy Z

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 Mountain trolls can occasionally be seen mounted on 
 Graphorns, though the latter do not seem to take 
 kindly to attempts to tame them and it is more 
 common to see a troll covered in Graphorn scars.
           -Fantastic Beasts and Where to Find Them
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