Indonesian volcanoes spewed hot ash, molten rock and clouds of dark smoke, and scientists warned that a violent eruption could happen at any moment.
The most threatening was Mt. Kelud on densely populated Java island, where a dome of magma was forming under a crater lake and soaring temperatures overheated monitoring equipment.
A few hundred miles away, Anak Krakatoa, or "Child of Krakatoa," fired pumice and lava onto its slopes off the northern tip of Java. At least one other volcano also showered ash on villages in Indonesia, which has many active volcanoes.
Authorities monitoring the peaks were most worried about Kelud because of its deadly history, including a 1919 explosion that killed thousands. Scientists have been warning since Friday that an eruption was imminent based on the frequency of tremors and its intense heat.