Japan orders inspection of road tunnels after fatal cave-in

Japan yesterday ordered inspections of ageing motorway tunnels after a cave-in that killed nine people, with suspicion over the cause of the accident focused on decaying ceiling supports.

The government pledged a thorough review and said "significant investment" is likely to be required in the motorway network, parts of which, including the accident site, were built during the economic boom of the 1960s and 1970s.

"As a major factor, we suspect ageing," an official from highway operator NEXCO said, referring to Sunday's tragedy at the Sasago tunnel which passes through hills near Mount Fuji 80 kilometres west of Tokyo.

Engineers yesterday began inspections at three other tunnels in the region with the same design, as well as the Sasago carriageway. There are reportedly around 20 such tunnels nationwide .

Footage from inside the tunnel showed concrete panels had collapsed in a V-shape, possibly indicating some kind of weakness in the central supporting pillars suspended from the roof, experts said.

NEXCO said safety inspections consist largely of visual surveys, with workers looking for cracks and other abnormalities, or listening to the acoustics of the concrete and metal parts by hitting them with hammers.