The anomalies in the conductivity and thermopower associated with the charge-density-wave instabilities of 2D Bloch electrons in magnetic fields are studied. It is assumed that the electrons are scattered elastically by randomly distributed impurities. The minimum of the conductivity sigma _xx and the maximum of the thermopower Q_xx are split into several minima and maxima in the same way as the Van Hove singularities after the lattice distortion takes place. If the electron scattering is anisotropic (low angle) the results are essentially the same as in the case of isotropic scattering, with the only difference being that sigma _xx is multiplied by a large factor.