TOKYO - An unknown number of vehicles were ablaze inside a collapsed motorway tunnel -- one of the longest in Japan -- outside Tokyo on Sunday, police said, as a full-scale emergency operation swung into action.
At least three vehicles were crushed and three people were injured in the accident, public broadcaster NHK said, but the report could not be immediately confirmed by police and fire department officials.
The accident occurred on Tokyo-bound lanes inside the Sasago tunnel on the Chuo Expressway, some 80 kilometres (50 miles) west of the capital, at around 8:00 am (2300 GMT Saturday), an official at the expressway traffic police unit told AFP.
"We don't know exactly how many vehicles are on fire," he said by telephone.
NHK footage from inside the tunnel showed a white ambulance and several firefighters wearing protective gear, working in an section shrouded in white smoke. A number of cars with lights flashing were also seen.
A 28-year-old woman was taken to hospital by ambulance after she emerged from the 4.3-kilometre-(2.7-mile)-long tunnel by herself, the traffic police official said.
NHK said two other women were rescued from inside the tunnel and that the extent of their injuries was unknown.
A reporter for NHK said he happened to be driving through the tunnel on his way to Tokyo when it started to disintegrate.
"I managed to drive through the tunnel but vehicles nearby appeared to have been trapped," he said. "Black smoke was coming and there seemed to be a fire inside the tunnel."
The thick smoke inside the tunnel was hampering rescuers' attempts to reach the caved-in point, some two kilometres (1.3 miles) from the Tokyo-side exit, a local fire department official said.
"The tunnel's smoke ventilation system is malfunctioning and we can't see anything one metre in front," Kazuya Tezuka told AFP by telephone.
Aerial footage on NHK showed several red trucks from the local fire department waiting outside the Tokyo side of the tunnel.
Dozens of people were seen waiting at an expressway bus stop just outside the exit, and were believed to have exited from the tunnel, NHK said.
The 28-year-old women who made her way out of the tunnel told the fire rescue unit she had been riding in a rented van with five other people, Tezuka said.
"I have no idea about what happened to the five others. I don't know how many vehicles were ahead and behind ours," she was quoted as saying.
A man in his 30s, who was just 50 metres ahead of the caved-in spot when the accident happened, told NHK: "A concrete part of the ceiling fell off all of a sudden when I was driving inside. I saw a fire coming from a crushed car. I was so frightened I got out my car right away and walked one hour to get outside."
"The traffic was not so heavy," he added.
A stream of people was seen coming out of the other exit after abandoning their vehicles in the tunnel, NHK said.
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