Microwave losses due to conductivity and magnetic permeability are investigated in La_0.9Ca_0.1MnO₃ films illuminated with photons in the energy range of E=0.5-2 eV. Growth of photoinduced ferromagnetic hysteresis is observed when the magnetic field is swept between -15 and 15 mT at temperatures below 60 K. The time required for saturation of the opening of the hysteresis loop depends on the photon energy having the minimum of ≈40 s at the illumination intensity I=3.5×10¹⁴ photons/cm²s. Both photoinduced magnetization and the increase of microwave photoconductivity can be well explained with a model assuming that small ferromagnetic regions exist within an insulating ferromagnetic phase of the sample and that these regions are expanded by optically induced charge transfer between Jahn-Teller split e_g states of neighboring Mn³⁺ ions.