Four workers were missing after an apparent volcanic explosion Saturday near a highway tunnel under construction in central Japan.
Initial reports indicated a vast amount of steam, hot water and dirt burst out of the ground with a loud bang and shot as high as 30 yards, police in Nagano prefecture said.
The gushing subsided somewhat, but hot water was blasting through the ground in a dozen or so other spots, preventing police and rescue workers from approaching.
The accident occurred in an uninhabited, mountainous area about four miles from the nearest community, a hot spring resort called Sakamaki Onsen.
The area, which is highly volcanic and has many hot spring resorts, is about 190 miles west of Tokyo.