The tunnel , which was about 1.2 m ( 4 ft ) high by 0.9 m ( 3 ft ) wide , extended more than 1 km ( 0.62 mi ) beyond the MDL into South Korea .
The tunnel , which was about 1.2 m ( 4 ft ) high by 0.9 m ( 3 ft ) wide , extended more than 1,000 m ( 1,100 yd ) beyond the Military Demarcation Line ( MDL ) into South Korea .