The magnetic properties of the cubic NaZn13 type pseudobinary compounds La(TxSi1-x)13 were studied for T = Fe, Co and Ni in the temperature range 4.2-300 K. 57Fe Mössbauer spectroscopy was performed on LaFe11Si2 and 57Fe-doped LaCo11Si2. The compounds with T = Fe or Co are ferromagnetic, while the compound LaNi11Si2 is a Pauli paramagnet. The critical behaviour around the Curie temperature Tc was studied in La(FexSi1-x)13 by measuring the temperature dependences on the zero-field susceptibility and the electrical resistivity. The critical exponent γ in the expression χ ∝ (T - Tc)-γ was found to be close to 1.38 corresponding to an isotropic Heisenberg ferromagnet. The anomalous critical behaviour shown by electrical resistivity can be explained in terms of lattice softening associated with the Invar effect.