Experts voiced guarded optimism Monday that a life-threatening eruption of Mount Sakurajima is not imminent, despite the volcano's dramatic outburst in Kagoshima Prefecture the previous day.

Sakurajima, a quasi-island next to the city of Kagoshima, is in a virtually constant state of eruption and has logged 500 outbursts so far this year.

Sunday afternoon's explosion sent a plume of smoke and ash 5 km into the sky, this time from the volcano's Showa vent, which became active in 2006 after years of dormancy. The plume's altitude was the highest from the Showa vent ever recorded, said the Meteorological Agency, which started collecting data in 2006.