CNN — An unknown number of cars were trapped early Sunday after a tunnel collapsed some 50 miles (80 kilometers) west of Tokyo, police said.
The cause of the collapse was not immediately clear, nor was the number of people potentially affected.
The Sasago tunnel is located on the Chuo Expressway. According to Otsuki police, the cave-in occurred on the Tokyo-bound lanes.
The road was temporarily closed and authorities were working to rescue victims, police said.