We present experimental and numerical studies of nonlinear magneto-optical rotation (NMOR) in rubidium vapor excited with resonant light tuned to the $5^2!S_{1/2}rightarrow 6^2!P_{1/2}$ absorption line (421~nm). Contrary to the experiments performed
to date on the strong $D_1$ or $D_2$ lines, in this case, the spontaneous decay of the excited state $6^2!P_{1/2}$ may occur via multiple intermediate states, affecting the dynamics, magnitude and other characteristics of NMOR. Comparing the experimental results with the results of modelling based on Auzinsh et al., Phys. Rev. A 80, 1 (2009), we demonstrate that despite the complexity of the structure, NMOR can be adequately described with a model, where only a single excited-state relaxation rate is used.
