Concrete ceiling slabs fell onto moving vehicles deep inside a long Japanese road tunnel, and authorities confirmed nine deaths before suspending rescue work while the roof was being reinforced to prevent more collapses.
Two vehicles caught fire in the accident, and heavy smoke initially hindered rescue efforts.
The location of the accident about a mile inside the three mile long Sasago Tunnel was also making the work difficult.
The nine dead were travelling in three vehicles in the tunnel about 50 miles west of Tokyo on a road that links the capital to central Japan.
The tunnel opened in 1977 and is one of many in the mountainous country.
The search was suspended while the road operator does work to support the remaining slabs in the ceiling, said Jun Goto, an official at the Fire and Disaster Management Agency. It is expected to resume later.
Police and the road operator Central Japan Expressway Co were investigating why the concrete slabs collapsed. An inspection of the tunnel's roof in September found nothing amiss, according to Satoshi Noguchi, a company official.
An estimated 270 concrete slabs, each weighing 1.4 metric tons, suspended from the arched roof of the tunnel fell over a stretch of about 120 yards, Mr Noguchi said.
The operator was exploring the possibility that bolts holding a metal piece suspending the panels above the road had become aged, he said. The panels, measuring about 16 feet by four feet, and three inches thick, were installed when the tunnel was constructed in 1977.
Company President and chief executive Takekazu Kaneko said that the company was inspecting other tunnels of similar structure, including a parallel tunnel for traffic going in the opposite direction. Both sections of the road were shut down indefinitely. Two people suffered injuries in the collapse.