Japan has ordered emergency inspections of highway tunnels across the country after one collapsed killing nine people.
Two people were also injured when a 110 metre-long section of the tunnel's concrete ceiling panels collapsed onto cars yesterday along the Chuo Expressway in Yamanashi prefecture, about 80km west of Tokyo.
An official from the highway operator said the metal rods used to secure the concrete panels to the walls in the 4.7km tunnel may have become loose.
"The prime minister ordered the transport ministry to put the utmost efforts into rescuing victims, to quickly investigate the cause of the accident and to establish measures to prevent similar accidents, and to provide a counselling service to victims to take care of them," chief cabinet secretary Osamu Fujimura told a news conference.
The Land Ministry ordered highway companies with similar concrete panels in tunnels to make emergency inspections.
The ceiling panels had not been repaired or reinforced since they were built in 1977 but passed safety checks in September, public broadcaster NHK reported.
In 1996 a tunnel in Hokkaido, northern Japan, collapsed and falling rocks crushed cars and a bus, killing 20 people.