Nine bodies -- eight of them burned -- have been pulled from vehicles crushed in a tunnel collapse about 80 kilometers (50 miles) west of Tokyo, highway police said Monday.
The disaster has prompted Japanese authorities to order emergency checks on dozens of other tunnels across the country that have a similar design, as questions were raised about whether aging parts may have contributed to the collapse.
Five of the bodies were recovered in one charred station wagon, and three others were in another burned vehicle, according to a police spokesperson. The other fatality was in a truck.
The Sasago tunnel on the Chuo Expressway remained closed Monday morning, one day after the cave-in occurred on the highway's Tokyo-bound lanes, police from the nearby city of Otsuki said.
Japanese highway police said Monday that the section of concrete that fell was 110 meters (360 feet) long, Earlier, officials from the East Yamanashi Fire Department said it was about 50 to 60 meters (160 to 200 feet) long and about 20 centimeters (8 inches) thick.
"Cars in front of us were crushed. It was terrifying," a man who witnessed the collapse told CNN affiliate TV Asahi.
"I don't think I could ever drive through the tunnel again," he said.
Soon after the collapse, Japanese public broadcaster NHK aired images showing smoke rising, a blue car with its side smashed in, and emergency vehicles on the scene.
Crews worked through the night as snow fell outside, trying to get to victims. All the while they were wary that the tunnel might collapse further.
The Japanese Ministry of Land, Infrastructure, Transport and Tourism said it had ordered emergency inspections of about 49 tunnels nationwide that have a ceiling structure similar to that of the Sasago tunnel.
The privately held Central Nippon Expressway Company operates the 4.7-kilometer-long Sasago tunnel, among others, as well as expressways and toll roads around Japan.
Some of the bolts on the on the fallen concrete slabs had dropped off, a company executive, Ryoichi Yoshizawa, said at a news conference Monday in Nagoya.
"The aging of the bolts or the concrete slabs could be a potential cause," Yoshizawa said, according to company spokesman Takayuki Ohmasa, who relayed the comments.
Yoshizawa told reporters that company maintenance teams had carried out regular visual checks on the ceiling that collapsed but had not done physical checks, like knocking on the bolts and slabs.
The Chuo Expressway is a particularly busy stretch of highway that runs between Tokyo and, among other places, Mount Fuji.
While it is a distance from the Japanese capital, the partial tunnel collapse and its subsequent closure are expected to cause major traffic disruptions, especially for those who rely on the expressway for business.
Authorities have not given any indication of when they expect the tunnel to reopen.