The structural, electrical, and magnetic properties of ceramic perovskite manganites LaMnO₃₊δ (δ = 0-0.154) are investigated. It is found that, in a weak magnetic field ( B = 2 G), the LaMnO₃₊δ manganite with δ= 0.065 at temperatures below the Curie temperature Tс of the paramagnet -ferromagnet phase transition has a mixed (spin glass + ferromagnet) phase. In LaMnO₃₊δ manganites with the parameter δ = 0.100-0.154, this phase transforms into a frustrated ferromagnetic phase. A similar transformation was observed previously in La₁₋ₓ CaₓMnO₃ сompounds at calcium contents in the range 0 ≤ x ≤ 0.3