Officials have widened a no-go area ringing Japan's Mount Kirishima volcano asthe pace of an ongoing eruption cycle quickened on Tuesday.Tuesday's blast was reportedly the fourth since Jan. 26.

Officials in Takahara have asked residents of about 500 households to evacuatedue to the threat of landslides and flying rocks blasted out of the Shinmoedakecrater. The affected area was within a 4-km (2.5-mile) radius of the activecrater. On Monday, 610 people had already been evacuated.

Local authorities said that airborne rocks, blasted aloft by the volcano, hadcarved impact craters as much as 8 feet (2.5 meters) deep within 3 km (1.8miles) of the Shinmoedake. Windows were also reportedly shattered in nearbyhouses and schools.

The local meteorological observatory stated, citing satellite images, that alava dome in the Shinmoedake crater had widened markedly between Thursday andSaturday.

Active lava domes can pose a serious threat of catastrophic explosion andcollapse.

The Kirishima volcanic complex is located on the southwestern mainland islandof Kyushu, north of Kagoshima city.

Craters of Kirishima Volcano onKyushu, Japan (Smithsonian National Museum of Natural History).Story by Jim Andrews, AccuWeather.com Senior Meteorologist.