The 1,330-foot peak in the Sunda Strait shot volcanic materials and ash up to 400 meters (1,300 feet). Wind carried the dust about 80 kilometers (50 miles) west to Banda Lampung in southern Sumatra.

State volcanologist Surono said Tuesday glowing material fell just around the slopes and volcanic activity has decreased.

He called on people living on both sides of the strait nearest the island to stay calm. The warning area is within one kilometer (3/5 miles) of the island.

Anak Krakatau, or "Child of Krakatau," rose from the sea in 1930 due to same tectonic forces that caused the 1883 Krakatau eruption that killed some 36,000 people.