JAKARTA — The death toll on the Indonesian island of Sulawesi from twin disasters, a major earthquake and the tsunami that followed, jumped to more than 800 on Sunday as rescue workers began to take stock of the wreckage — pulling out survivors buried under the rubble from a collapsed hotel, treating patients in tents and racing to get food and water to survivors.

Most of those killed were in the city of Palu, a spokesman for Indonesia’s National Disaster Management Agency, Sutopo Purwo Nugroho, said during a news conference Sunday. But just 11 deaths were reported from Donggala, a town of 300,000 that has been largely cut off from rescuers, with poor communications. Officials have warned that the death toll could rise to the thousands.

“The death toll is believed to be still increasing since many bodies were still under the wreckage” and others were out of reach, Nugroho said. The dead, he said, either drowned when the tsunami hit or were killed by collapsed buildings and rubble.

Photos on his Twitter account show bodies lined up in bags, as police begin the grim task of identifying them and reporting to their families. Victims are being buried in mass graves, but all victims will later be “buried properly,” Nugroho said.

A 7.5-magnitude earthquake triggered the massive tsunami Friday evening that crashed into Palu, Donggala and the surrounding settlements. Officials on Sunday shared chilling videos and photos on social media of land “liquefaction” in the wake of the disaster, during which the soil turns into something akin to quicksand and drags buildings into it. 

Even as relief efforts were underway, questions remained about the apparent failure of a warning system and a tsunami alert that was quickly dropped by the Indonesian geophysics agency.

The scene after an earthquake and tsunami strike Indonesia

A tsunami wave hits shore in Palu, Indonesia, on the island of Sulawesi. (SOCIAL MEDIA)

In the city of Palu, rescue teams were evacuating almost 50 people trapped in the ruins of the Roa Roa Hotel, a 50-room, eight-story building that collapsed after the earthquake. Several people were pulled out alive, and rescuers could hear the screams and cries of others throughout the night and see lights shining from cellphones underneath the rubble. A correspondent for a local newspaper wrote on his Facebook page that at least three other hotels with guests in them have also collapsed. Heavy equipment able to move rubble was on its way to the city.

Traumatized victims, many of whom were sleeping in tents and being treated for injuries outside their homes, continued to be shaken by aftershocks. At least 200 have hit the area since the quake, according to local officials.

Whenever there are aftershocks, people have “become panicked, running away with some yelling ‘Tsunami!’ ­­” said Radika Pinto, a manager in Palu for World Vision, a Christian aid group. 

Hungry survivors have been going into unstable shopping centers to take food, clothing and water. Adding to the chaos, local media outlets have reported that a prison wall collapsed, setting free hundreds of inmates. 

The head of Palu Penitentiary, Adhi Yan Ricoh, told the Indonesian magazine Tempo that more than half of the 560 inmates at the prison escaped.

“At that time, the electricity went out, and there were only a few officers,” Adhi said. “They also panicked and tried to save themselves.”

Nugroho, the disaster agency’s spokesman, said a Hercules C-130 plane was deployed to the area to evacuate the hordes racing to get out of the city. Water, he added, was an urgent need. 

“The water turned turbid and cannot be consumed. Clean water is an urgent need for the people of Palu,” he said. 

Thousands of homes, hotels, shopping centers, hospitals and other public facilities were damaged, Nugroho said. Hospital patients in Palu are being treated outside to avoid the danger of aftershocks. 

International relief agencies were just starting to reach the area on Sunday, after hours-long overnight drives through landslide-prone areas and badly damaged roads. Dozens of calls made to residents and hotels in Palu were unsuccessful, an indication that widespread communication outages continue.

Nugroho blamed the rising death toll on a lack of warnings and “limited shelter and spatial planning.”

“There is no sound of siren,” he said. Hundreds of people who were gathered on the beach for a festival didn’t know there was tsunami risk, he said.

The head of Indonesia’s geophysics agency, Dwikorita Karnawati, said her agency im­mediately issued a tsunami warning after the earthquake. The agency estimated the tsunami would occur at 5:22 p.m. local time. But it ended the tsunami warning at 5:36 p.m., prompting criticism that it was lifted too soon. Officials say the tsunami had struck by the time the alert was removed.

“We ended the tsunami warning when the tsunami happened,” Karnawati said.

Videos circulating online showed residents still milling around the beach, unconcerned, as those on higher ground tried to warn them. 

Indonesia is prone to earthquakes because of its location on the “Ring of Fire,” an arc of volcanoes and fault lines in the Pacific Basin.

In December 2004, a 9.1-magnitude earthquake off Sumatra in western Indonesia triggered a tsunami that killed 230,000 people in a dozen countries.

Mahtani reported from Yangon, Myanmar.