We present a numerical investigation of the light scattering in an absorbing medium with randomly distributed scatterers. The extinction coefficient is derived from an ensemble of numerical solutions of Maxwell's equations for many different realizations of the system. Results are in good agreement with the predictions given by the effective medium theory under the independent-scattering approximation. Beyond the independent-scattering approximation, we explore the domain of validity of an effective medium theory that takes into account correlations between pairs of scatterers. A good agreement is obtained with a filling ratio up to 30% for scatterers with a relative refractive index contrast lower than 20% and size parameters near unity.