Rescuers raced against the clock and a lack of equipment to save those still trapped in the rubble, with up to 60 people feared to be underneath one Palu hotel alone.
Rescue teams are trying to dig out many victims believed buried in mud in an Indonesian city devastated by Friday's quake and tsunami, which killed more than 800 people.
Disaster agency spokesman Nugroho told reporters on Sunday none of Indonesia's tsunami buoys, one device used to detect waves, had been operating since 2012.
Most of the casualties were caused by the quake itself and a deadly tsunami that slammed into the coastline around Palu.
Indonesia's Metro TV on Sunday broadcast aerial footage from a coastal community in Donggala, close to the epicentre of the quake.
Heavy machinery was also on the way from other areas on Sulawesi. Communication is still down, power is still out.
The grave being dug in Palu will be 10 by 100 meters and can be enlarged if needed, said Willem Rampangilei, chief of Indonesia's National Disaster Mitigation Agency.
In one devastated area in Palu, residents said dozens of people could still be buried in their homes. "We need all the help we can get", he said.
The death toll from Indonesia's quake and tsunami disaster almost doubled to 1,200 on Sunday (Sept 30) and was expected to rise further, prompting authorities to announce mass burials in a desperate attempt to stave off disease.
Indonesian Vice President Jusuf Kalla said the final number of dead could be in the "thousands" as many regions have still not been reached.
President Widodo visited a devastated housing complex on Sunday and called for patience. "My house is destroyed and I can't even give him his own funeral", said Rosmawati Binti Yahya, 52, whose husband was among those placed in the grave. Numerous aftershocks have rattled the region.
The dead - many yet uncounted, their bodies still trapped in the rubble of collapsed buildings - are also a source of concern for authorities.
"There are estimated to be many victims in this area". The buoys had been donated by the US, Germany, and Malaysia after the 2004 tsunami that killed nearly 250,000 people in the Aceh region, but they had been neglected, and many had been stolen or vandalized.
Internal affairs minister Tjahjo Kumolo, asked about reports of sporadic looting, said he had ordered authorities to help people get food and drink and businesses would be compensated.
By Saturday, they had rescued 11 adults, including a pregnant woman, and two other children - although one later died.
Sutopo said aid supplies had began arriving in Palu and were being distributed to those in need. The government has allocated 560 billion rupiah (S$51 million) for the recovery.
Local residents affected by the quake and tsunami wait to be airlifted out by military planes at Mutiara Sis Al Jufri Airport in Palu, Central Sulawesi, Indonesia September 30, 2018 in this photo taken by Antara Foto.
In December 2004, a massive magnitude-9.1 natural disaster off Sumatra in western Indonesia triggered a tsunami that killed 230,000 people in a dozen countries.
Meanwhile, questions are being raised about why the country's meteorological agency lifted the tsunami warning just over half an hour after the quake, possibly making a bad situation worse.