Filling dependence of magnetotransport properties was investigated in Ndl−xSrxMnO3 films. Hysteretic behavior was observed in temperature dependencies of resistivity for restricted filling of x-0.35 and 0.50, indicating the occurrence of a first-order phase transition at low temperatures. The transition gives rise to a high-resistivity state which collapses to low-resistivity state under an external magnetic field. Change in resistivity by applying magnetic field was more than a order of magnitude. Origin of colossal magnetoresistance (CMR) is briefly discussed in terms of such a first-order phase change induced by a magnetic field.