Agency chief Willem Rampangilei says the grave will be 10 meters by 100 meters (33 feet by 330 feet) in size, and can be expanded if needed.
He said a mass burial would be held on Sunday for health reasons.
"We hope there will be global satellites crossing over Indonesia that can capture images and provide them to us so we can use the images to prepare humanitarian aid", Nugroho said.
The horrific scene began on Friday afternoon when a series of tremors rocked Sulawesi and a 7.5 magnitude quake triggered a tsunami that sent waves of "about 10 feet high" to the beaches of Palu and Donggala.
President Joko Widodo visited Palu on Sunday to inspect the rescue.
Dozens of people were reported to be trapped in the rubble of a hotel and a mall in the city of Palu. "I could do nothing to help", resident Nur Indah said, crying. - 75,000 people exposed to MMI VII "Very Strong" shaking (Moderate damage to vulnerable structures) Tsunami risk: The event happened very close to the coast: a moderate tsunami of the order of 1m can be produced along the coasts of Sulawesi, with the current parameters. Others offered her food and water.
Two months ago, on another Indonesian island - Lombok - a series of earthquakes, in which more than 500 people were killed. He said that "God consoles them and supports the efforts of those who are working to bring aid". Officials had estimated about 50 people could be inside.
Communications with the area were hard because power and telecommunications were cut, hampering search and rescue efforts.
Hospitals were overwhelmed by the influx of injured, with many people being treated in the open air, while other survivors helped to retrieve the remains of those who died.
The initial quake struck as evening prayers were about to begin in the world's biggest Muslim majority country on the holiest day of the week, when mosques are especially busy.
Other rescuers worked to free a 15-year-old girl trapped under concrete in her house in Palu after it collapsed on her family during the magnitude 7.5 quake that spawned a tsunami.
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Indonesia's president said on Friday night that he had instructed the security minister to co-ordinate the government's response to the quake and tsunami.
Earthquakes of this size can often have a deadly impact on nearby communities.
Jokowi said Sunday in the hard-hit Sulawesi island city of Palu that the city's airport "is not 100 percent ready for landing".
"There are many challenges", he said.
Another 6.1 magnitude quake had hit the same area just hours earlier. Another 11 people are confirmed dead in the regency of Donggala.
It's the latest natural disaster to hit Indonesia, which is frequently struck by earthquakes, volcanic eruptions and tsunamis because of its location on the "Ring of Fire", an arc of volcanoes and fault lines in the Pacific Basin.
He also said 61 foreigners were in Palu at the time of the disaster, and most have been accounted for. Three visitors from France and one from Malaysia are missing.
Friday's tremor was also felt in the far south of the island in its largest city Makassar and on neighbouring Kalimantan, Indonesia's portion of Borneo island.
Authorities fear that the death toll could continue to rise quickly. He said another 11 people were killed in the regency of Donggala. The regencies of Donggala, Sigi and Parigi Moutong - with a combined population of 1.2 million - had yet to be fully assessed.
He says: "The death is believed to be still increasing since many bodies were still under the wreckage while many have not able to be reached". The water smashed into buildings and a large mosque already damaged by the quake.