A Japanese volcano erupted this morning, trapping hundreds of hikers and possibly killing one person. A massive cloud of ash now covered the immediate region, stretching for nearly two miles, according to local reports.

"It was like thunder," one woman told local broadcaster NHK via The Weather Channel. "I heard boom, boom, then everything went dark."

According to updates from Reuters and the Agence France Presse (AFP) well over 250 people were initially trapped on Mount Ontake when it unexpectedly erupted Saturday morning, possibly killing one woman and injuring 30 others. More than 10 remain unconscious - likely from asphyxiation.

An estimated 20 to 40 people are thought to be still trapped on the mountain, taking shelter from suffocating ash in rest lodges along the mountain. No dangerous lava flow has been identified after the initial explosion, but the ash alone has been reported to being up-to eight inches thick on some parts of the mountain.

You can watch a video taken by startled hikers scrambling to descend the mountain below. (Scroll to read on...)

[Credit: kuroda terutoshi]

Mount Ontake is traditionally a popular hiking spot at the start of the autumn season, as it provides paths for climbers to admire the stunning colors of turning leaves.

Prime Minister Shinzo Abe, who returned from the United States on Saturday, said he has ordered the Japanese military to help in rescue efforts already underway thanks to Nagano prefecture's police.

"I instructed to do all we can to rescue the people affected and secure the safety of the trekkers," Abe told local media in brief conference.

 NHK World reports that 230 people have already been rescued so far with the remaining hikers expected to descend tomorrow morning, after most of the ash settles. Fire department officials initially told media that a women was confirmed dead, but they later retracted the announcement.

This eruption was relatively unexpected, with no noteworthy earthquake swarms - characteristic of rising volcanic activity - occurring before the blast. The Japan Meteorological Agency has elevated the warning levels for three volcanoes in all to code orange, meaning "do not approach."