Screw got magnetized to a PC part

[WolfRayet O]

Hi,
I was working on my PC to install a GPU and then two of the attachment screws fell and it sounded like it got magnetized to something.
Also I try to shake the the PC and can't hear the screws.
What PC parts are magnetic??

 

[Ecky]

Normally there's a small magnet inside of mechanical hard drives, and one in the hub of each fan.There shouldn't be any others.