Many of the electric and magnetic properties of superconductors are determined by the behavior of flux vortices. Transport current flowing through a superconductor exerts a force on these vortices and if it is strong enough to overcome pinning from material defects, vortices will start to flow. This flow is dissipative and, as such, destroys the superconductor's fundmantal property of perfect conductivity. Thus, the manipualtion of the pinning potential has attracted much attention in both technological and fundamental aspects. In this work we injected current from a normal metal (Al) into a thin film superconductor (Nb) through an array of nanometric contacts. We show that vortex flow exhibits avalanches, attributed to channels of flowing vortices through static vortex matter. An anomalous response to an applied magnetic field is observed when the system is on the verge of an avalanche. This vortex flow is contrasted with that observed in the same films when the current is made to flow only through the superconducting films. In the latter case no avalanches or anomalous response to field are observed. We suggest an interpretation for these results in the framework of local non-equilibrium quasiparticle excitations.