Authorities cautioned residents to stay away from the coast late Tuesday while volcanic activity as well as weather and sea conditions were monitored for tsunami risks. A massive wave that followed an eruption of the Anak Krakatoa volcano hit communities along the Sunda Strait on Saturday night, killing more than 430 people and displacing thousands.

Residents were asked to stay at least 1,640 feet from the Sunda Strait coastline, said Dwikorita Karnawati, the head of Indonesia's Meteorology, Climatology and Geophysics Agency. She said the wall of the volcano's crater was prone to collapse and could cause another massive wave.

At a news conference late Tuesday, Karnawati said weather and continuing eruptions "could potentially cause landslides at the cliffs of the crater into the sea, and we fear that that could trigger a tsunami."

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Meanwhile, heavy rains were affecting the ability of search and rescue teams to help those who remained stranded, as rescue workers warned that vital supplies like medicine and clean water were running low, the AFP news agency reported. Thousands of survivors were crammed into makeshift shelters and hospitals, causing some officials to warn of a possible public health crisis.

Indonesia, a vast archipelago of more than 17,000 islands and home to 260 million people, lies along the Ring of Fire, an arc of volcanoes and fault lines in the Pacific Basin. Saturday's tsunami was the third natural disaster in six months: Thousands were believed killed by an earthquake and tsunami that hit Sulawesi island in September, and, in August, an earthquake on the island of Lombok killed 505 people in August.

Wednesday marked the 14th anniversary of the Boxing Day tsunami, which killed approximately 220,000 people in countries around the Indian Ocean, 120,000 of whom were in Indonesia.