At approximately 8 a.m. on December 2, 2012, nearly 150 concrete ceiling panels inside the Tokyo-bound Sasago Tunnel collapsed, crushing three vehicles, including a van carrying six persons that caught fire. The fallen panels were 20 centimetres (7.9 in) thick and weighed 1.2 tons each. The caved-in point was 2 kilometres (1.2 mi) from the Tokyo-side exit and over a length of 50 to 60 metres (160–200 ft). Smoke could be seen billowing from the Kōshū entrance to the tunnel.
Nine people died and two were injured, making it the deadliest Japanese roadway accident in history. The tunnel was closed for a period of 27 days for repairs and removal of ceiling panels, before the south tube reopened on December 29. The north tube, where the collapse happened, reopened on February 8, 2013.