Part of a concrete wall inside a tunnel connecting Osaka and Wakayama Prefectures collapsed on Thursday, police said.
Police say that at around noon, a slab of concrete measuring 90 cm wide, 40 cm tall and 10 cm thick fell from a height of around 5 meters above the ground. The slab landed on the side of the lane and broke into pieces.
TV Asahi reported that nobody was injured in the incident, which took place on National Highway Route 371. A spokesperson said that inspections had been carried out of the roof of the tunnel prior to the incident, but not on the walls.