We consider the question of propagation of thermal perturbations in the carrier system in photoinjected plasma in semiconductors. A hydrodynamiclike approach is introduced in the spirit of extended irreversible thermodynamics (EIT) that incorporates the energy flux as a basic thermodynamic variable. Its equation of evolution is derived at the microscopic level using the nonequilibrium statistical operator method which provides the foundations for informational statistical thermodynamics. This equation is of the Maxwell-Cattaneo type of EIT, which replaces the Fourier constitutive equation of classical irreversible thermodynamics. Used in conjunction with the equation of conservation for the energy density, together with the definition of a nonequilibrium temperature, it leads to a wave equation with damping, implying the propagation of second sound. © 1995 The American Physical Society.52750305035