Indonesia’s disaster management officials on Monday warned of another tsunami after one struck without warning in areas around the country’s Sunda Strait on December 22, BBC reported.

The toll from the tsunami, which had hit the Sumatra and Java islands around 9.30 pm local time (8 pm Indian time) on Saturday, is now 281 and the number of injured is pegged at 1,061, said disaster agency spokesperson Sutopo Purwo Nugroho.

Rescue efforts are on to find 56 people who were reported missing and the toll is expected to rise, AP reported. The operation is being hindered by blocked roads.

Early reports indicated that the tsunami may have been caused by an abnormal tidal surge due to the new moon and an underwater landslide following the eruption of the Anak Krakatoa volcano, according to AFP. The Anak Krakatoa is known as the “child” of the Krakatoa, whose eruption in 1883 had killed 36,000 people and had sparked a tsunami that was felt around the world. The Anak Krakatoa is a small island in the Sunda Strait.

Nugroho said eruptions from the volcano make another tsunami likely. “Recommendations from [the] Meteorology, Climatology and Geophysical Agency are that people should not carry out activities on the beach and stay away from the coast for a while,” he added.

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Members of popular pop group “Seventeen”, which was performing in Banten, Java, when the tsunami hit Banten, confirmed the death of its guitarist Herman Sikumbang, crew member Rukmana “Ujang” Rustam and road manager Oki Wijaya. The band’s vocalist, Riefian “Ifan” Fajarsyah, shared the news on his Instagram page. He revealed that he was now waiting on news about the band’s drummer Andi Windu Darmawan. Ifan is also said to be looking for his wife Dylan Sahara, Jakarta Post reported.

Indonesian President Joko Widodo has flown to the disaster zone and is visiting hospitals in the Pandeglang area to comfort survivors, The Guardian reported.

This is the second tsunami to hit the country in three months. A 7.5 magnitude earthquake had struck off the Sulawesi island in September and caused a tsunami, killing hundreds of people. A series of earthquakes in July and August had killed nearly 500 people on the holiday island of Lombok.