The microscopic origin of electronic noise in intrinsic amorphous hydrogenated silicon (a-Si:H) is studied with noise-detected magnetic resonance (NDMR). This measurement technique, combining conventional noise spectroscopy and electron paramagnetic resonance (EPR), allows the identification of paramagnetic states involved in transport processes underlying electronic noise. The sensitivity of the setup is discussed and shown to be at the fundamental limit within a factor of 2. The NDMR results obtained from Cr-n+-i-n+-Cr a-Si:H sandwich structures show that holes in the valence band tail play a dominant role in the generation of low-frequency non-thermal noise in intrinsic a-Si:H.