We report the first reliable measurement of the nebular [OI] 5577AA emission line in the Orion nebula. The use of diagnostic diagrams using the nebular [OI] and [NI] lines and the comparison with available photoionization models, indicate that the bulk of the nebular emission of the neutral ionic species in the Orion nebula is produced in regions of low to moderate electron densities (10^3 -- 10^5 cm^-3) and electron temperatures of about 10000 K. This result is in disagreement with previous results presented in favor of very high-density regions in the partially ionized zone of the Orion nebula. The absence of such high-density zones has important consequences on the conditions where the [FeII}] emission is produced.