Japanese police say a highway tunnel collapsed early Sunday west of Tokyo, trapping an undetermined number of vehicles.

The incident at the Sasago tunnel occurred in the Tokyo-bound lanes of the Chuo Expressway, about 80 kilometers west of the capital.

There are early reports that some vehicles are on fire, but police had no estimates of casualties two hours after the 8 a.m. collapse.

Japan public broadcaster NHK says one of its reporters was driving through the tunnel as it began to disintegrate behind him. The journalist reported thick smoke and fire after making his escape.