  Detailed 57Fe M\"ossbauer spectroscopy measurements on superconducting NaFeAs
powder crystals have been performed. The 57Fe spectra recorded in the
paramagnetic temperature range (T > TN \approx 46 +/- 2 K) were discussed
supposing Fe2+ ions are located in distorted tetrahedral (FeAs4) polyhedra. Our
results reveal that the structural transition (TS \approx 55 K) has a weak
effect on the electronic structure of iron atoms while the development of the
antiferromagnetic order (T =< TN) induces a redistribution of the charge at
57Fe nuclei. In the low-temperature range, the spectra show a diffuse resonance
absorption structure which evidences for the existence of a continuous
distribution of hyperfine fields HFe at 57Fe nuclei. The shape of these spectra
can be related to the formation of a microdomain structure or phase separation.
Analysis of the resulting distributions p(HFe) has shown that the M\"ossbauer
spectra give consistent and physically reasonable 57Fe hyperfine parameters
over the whole temperature range.
