JAKARTA, Indonesia — More deadly tsunamis could strike the Indonesian coastline in the coming days, authorities warn, as the volcano which triggered the weekend’s devastating wave continues to erupt.

At least 281 people have died from the tsunami, which struck the Indonesian coastline without warning Saturday night. Hundreds more are injured and more than two dozen remain missing.

Eyewitnesses described fleeing for their lives as beachfront homes were swept away in the wave, which is thought to have been caused by underwater landslides following the eruption of the Anak Krakatau volcano.

Sutopo Purwo Nugroho, a spokesman at Indonesia’s National Disaster Mitigation Agency, warned Sunday that more tsunamis were possible as long as the volcano remained active.

“We are cautioning the people to remain cautious,” Sutopo said. “Agencies are still continuing to analyze the root cause … the Krakatau volcano continues to erupt, which could potentially trigger another tsunami.”

A crowd was watching Indonesian pop band Seventeen at a show organized by state-run electric company PLN at the Tanjung Lesun beach resort when the massive wave crashed through the stage and threw it into the audience.

The band’s bass player and manager were killed, lead singer Riefian Fajarsyah said in a tearful video posted on Instagram. Three other members of Seventeen and Fajarsyah’s wife — whose birthday is Sunday — are still missing, he said.

According to officials, 843 people were injured and another 28 are unaccounted for.

Daniel von Rège, head of mission in Indonesia for Doctors without Borders, said more bodies and injured people were expected to arrive at hospitals across the region over the coming days.

At least 558 houses were destroyed, while nine hotels, 60 restaurants and 350 boats were heavily damaged, an indication of the tsunami’s impact on residential and tourist areas.

No foreigners had been reported killed or injured.

Tsunami caused by underwater landslides

The tsunami is believed to have been triggered when the Anak Krakatau volcano erupted in the Sunda Strait between the islands of Java and Sumatra, prompting a series of underwater landslides, according to Indonesia’s Meteorology, Climatology and Geological Agency (BMKG).

When the displaced rock shifted beneath the water’s surface, it “pushed up” the water on top of it, CNN Meteorologist Allison Chinchar said, and generated the tsunami.

Anak Krakatau sits between the islands of Java and Sumatra.

The tsunami’s impacts were compounded by a tidal wave caused by the full moon, BMKG said in a news release.

Anak Krakatau is known for its 1883 eruption — one of the deadliest in recorded history — that killed more than 36,000 people.

Despite the devastating 2004 Boxing Day tsunami that killed hundreds of thousands of people, Indonesia lacks proper equipment to warn of an incoming tsunami threat.

“We need a multi-hazard early warning system,” said Nugroho. “And we need lots of it.”

Nugroho pointed out tsunamis are faster and less predictable than tidal waves, which are caused by atmospheric conditions.

“We used to know that a tsunami happens after an earthquake. There was no quake last night,” he said, referring to the sub-aquatic landslides. “That is why there was no warning.”

Prayers pour in from around the world

Pope Francis prayed for the tsunami victims at his regular Sunday Angelus service in St. Peter’s Square.

“I am spiritually close to the displaced and to all the people affected, imploring God for relief in their suffering,” he said. “My appeal is that these brothers and sisters may not lack our solidarity and the support of the international community.”

US President Donald Trump addressed the “unthinkable devastation” on Twitter Sunday morning. “We are praying for recovery and healing,” Trump wrote. “America is with you!”

The International Federation of Red Cross and Red Crescent Societies in Indonesia expects the death toll to rise, spokeswoman Kathy Mueller said. It’s providing support by bringing in basic household items, clean water and equipment to clear debris.

The UN World Food Programme also stood ready to support the Indonesian government, according to WFP spokeswoman Bettina Luescher.