We study the emission of photons from porous Si after high-level vibrational excitation in the Si-O absorption band using a pulsed CO2 laser. Narrow resonances in the efficiency of light generation are discovered at 1030 cm(-1) and 1084 cm(-1). For excitation at 1030 cm(-1) the familiar photoluminescence band of porous Si appears. Time-resolved pump-to-probe experiments show the same decay times for the photo and the IR-induced luminescence. We suggest a microscopic process responsible for the light emission.