Smoke billows out of the Sasago Tunnel on the Chuo Expressway in Koshu, Yamanashi Prefecture, central Japan after part of the tunnel collapsed. Photo / AP

Smoke billows out of the Sasago Tunnel on the Chuo Expressway in Koshu, Yamanashi Prefecture, central Japan after part of the tunnel collapsed. Photo / AP
A motorway tunnel has caved in 80km west of Tokyo, trapping an unspecified number of vehicles, press reports say.
The incident occurred on the Tokyo-bound lanes inside the Sasago tunnel on the Chuo Expressway at around 8am local time on Sunday, public broadcaster NHK and Jiji Press said.
An NHK reporter said the tunnel started to disintegrate when he was driving through it on his way to Tokyo.
"I managed to drive through the tunnel but vehicles nearby appeared to have been trapped," he reported.
Police said an unknown number of vehicles were ablaze inside the tunnel.
"We have limited information on the accident at the moment but smoke is said to be coming out from the tunnel as an unspecified number of vehicles were burning," an official at the local expressway traffic police unit told AFP by telephone.
A woman was taken to hospital by ambulance after she came out of the tunnel, the spokesman said.