A ceiling panel assembly for being secured to, and for concealing, a suspended inverted T-shaped, longitudinally extending main runner having a vertically disposed web, a horizontally disposed flange divided by the web to equal flange portions, and a protuberance at a terminal end of each of the flange portions, which comprises: a main section with a first and second lateral edge and visible panel sections and two support sections laterally extending in opposite directions, which are disposed above the main section. The two support sections releasably contact two adjacent and laterally spaced main runners, respectively, and one of the sections is adapted to multi-directionally stiffen a corresponding main runner.