Summary: Scenarios of the development of continuous families of steady-state regimes branching off from mechanical equilibrium are investigated for the plane problem of filtrational convection of a multicomponent fluid saturating a porous block of rectangular cross-section. Convection of two- and three-component fluids is considered, and unidirectional and differently directed vertical temperature and concentration gradients are analyzed. A new scenario of the formation of a continuous family of steady-state solutions realized in the case of oscillatory instability of mechanical equilibrium is studied.