How did a volcano possibly trigger Indonesia’s deadly tsunami?

Click to play video: 'Krakatoa eruption thought to be cause of deadly tsunami in Indonesia'
Krakatoa eruption thought to be cause of deadly tsunami in Indonesia
WATCH: Krakatoa eruption thought to be cause of deadly tsunami in Indonesia – Dec 23, 2018

A tsunami killed at least 222 people and injured hundreds in Indonesia following an underwater landslide that is believed to have been caused by the erupting Anak Krakatau volcano, officials said on Sunday.

Anak Krakatau, which lies roughly halfway between Java and Sumatra, has been spewing ash and lava for months.

It erupted again just after 9 p.m. on Saturday and the tsunami struck at around 9:30 p.m., according to Indonesia’s Meteorology, Climatology and Geophysics Agency, BMKG.

WATCH: Indonesia tsunami leaves over 200 dead

Click to play video: 'Indonesia tsunami leaves over 200 dead'
Indonesia tsunami leaves over 200 dead

The tsunami was caused by “an undersea landslide resulting from volcanic activity on Anak Krakatau” and was exacerbated by abnormally high tides because of the full moon, said Sutopo Purwo Nugroho, a spokesman for Indonesia’s disaster mitigation agency.

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Hundreds of homes and other buildings were heavily damaged when the tsunami struck, almost without warning, he said.

Anak Krakatau volcano is shown during an eruption at Sunda strait in South Lampung, Indonesia, Dec. 3, 2018 in a photo taken by Antara Foto. Antara Foto/Bisnis Indonesia/Nurul Hidayat/ via REUTERS

Ben van der Pluijm, an earthquake geologist and a professor in the University of Michigan, said the tsunami may have been caused by a “partial collapse” of Anak Krakatau.

READ MORE: Tsunami wave crashes into concert on Indonesian beach, killing 2 band members: video

“Instability of the slope of an active volcano can create a rock slide that moves a large volume of water, creating local tsunami waves that can be very powerful. This is like suddenly dropping a bag of sand in a tub filled with water,” he said.

The tsunami forced thousands of residents to evacuate to higher ground. By late afternoon on Sunday, the disaster agency had raised the death toll to 222, with 843 injured and 28 missing.

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Coastal residents reported not seeing or feeling any warning signs on Saturday night, such as receding water or an earthquake, before waves of 2-3 metres washed ashore, according to media.

The eruption of Krakatau, previously known as Krakatoa, in 1883 killed more than 36,000 people in a series of tsunamis.

Anak Krakatau, which means child of Krakatau, is the island that emerged from the area once occupied by Krakatau, which was destroyed in 1883.

It first appeared in 1927 and has been growing ever since.

WATCH: Hospitals overwhelmed following deadly tsunami in Indonesia

Click to play video: 'Hospitals overwhelmed following deadly tsunami in Indonesia'
Hospitals overwhelmed following deadly tsunami in Indonesia

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