Recently, we have found a new multiferroics material FeTe2O5Br, with simultaneous ferroelectric and incommensurate magnetic orderings appear at TN = 11 K. Our neutron diffraction data suggest that the structure is amplitude modulated, but a helical magnetic arrangement cannot be ruled out. We propose to distinguish between the two models by local-scale muon spin relaxation experiments, since spin dynamics is expected to be drastically different in the two states. The distinction is very important in identifying the mechanism leading to magneto-electric coupling in this material, which might constitute a new class of multiferroics.