We report the application of pump-probe second harmonic generation (SHG) to monitor spin dynamics in nonmagnetic semiconductor heterostructures. Spin-polarized electrons were selectively excited by a pump beam in the GaAs layer of GaAs/GaSb/InAs structures. However, the induced magnetization manifests itself through the SHG probe signal from the GaSb/InAs interface, thus indicating a spin-polarized electron transport. We find that the magnetization dynamics is governed by an interplay between the spin density evolution at the interfaces and the spin relaxation. © 2002 American Institute of Physics.