One of Japan's most active volcano sites Mount Aso erupted on Monday. The eruption sent a cloud of thick black smoke and ash over a mile into the air disrupting flights.

Japan's NHK news agency reported, at the time of eruption, around 100 tourists and other visitors were present in the surrounding area of Aso, which is a well know hiking destination, but they were quickly whisked away to safety.

There is a ropeway transit station over a half-mile away Aso, it was covered in volcanic. Aso police station told NBC News that around 20 people who were present in the station during the eruption were safely evacuated.

As per the Japan Meteorological Agency, the Aso eruption took place without any warning at around 9:43 am in one of the Nakadake craters at Mount Aso, on the southwestern island of Kyushu. The agency issued a level 3 alert and warned people to avoid coming to this area.

The agency's senior coordinator for volcanic affairs, Sadayuki Kitagawa has given a warning that another eruption was possible ‘with risk of volcanic rocks landing in an area of more than a 1-kilometer radius’, or about six-tenths of a mile. He has warned people to stay vigilant for flying rocks and ash within a 2-kilometer radius.

According to Japan Air Lines, arrivals and departures at Kumamoto Airport were ‘irregular’ due to the eruption. The airline mentioned that a number of flights had already been canceled, and more cancellations were expected.