Most of the bodies have not been claimed but some relatives turned up to pay respects to loved ones at the 50m trench, where the smell of decomposition was overpowering.
This would help explain why the waves were so big near Palu, but much smaller in the surrounding area.
Sumba lies some 1,600km to the south of Sulawesi island which was struck by a devastating quake and tsunami on Friday, killing more than 800 people.
Commercial airlines have struggled to restore operations at Palu's quake-damaged airport, but military aircraft took survivors out on Monday.
In Balaroa, a Palu suburb once home to a housing complex, the scale of the damage was obvious. A wasteland of flattened trees, shards of concrete, twisted metal roofing, door frames and mangled furniture stretched out into the distance.
Inmates had fled from another overcapacity facility in Palu by breaking down its main door and another in Donggala, an area also hit by the disaster.
Indonesia has agreed to accept international help and will coordinate private sector help from around the world.
Dozens of aid agencies and NGOs have lined up to provide live-saving assistance as Jakarta struggles to come to terms with the sheer scale of the disaster.
Grim warnings came that the eventual toll could reach thousands.
Indonesians took to social media to question the BMKG's move to lift the tsunami warning and a failure to release information in a timely manner.
The quake hit central Sulawesi island at a shallow depth of some 10 kilometres (six miles), just hours after a smaller quake killed at least one person in the same part of the country.
Indonesia, one of the most disaster-prone nations on earth, straddles the so-called Pacific 'Ring of Fire', where tectonic plates collide and many of the world's volcanic eruptions and earthquakes occur.
Women and children are among the 128 people found to have been infected with malaria.
Japan's trade minister Hiroshige Seko calls on the island's businesses and 5.3 million residents to use about 20% less energy to prevent further blackouts.
22 people remain unaccounted for in the small northern countryside town of Atsuma.
An earlier tremor of 6.3 magnitude struck the island earlier in the day, where an earthquake earlier this month killed more than 430 people.
Lombok's northern region has been hardest hit, where 374 people died and more than 137,000 have been forced from their homes, according to the latest official tolls.
The national disaster mitigation agency said it had verified 321 deaths and that over 270,000 people had been forced to flee their homes because of a series of tremors over the past two weeks.
Reuters witnesses reporting said buildings and walls that had already been weakened collapsed, and people ran out onto roads even as rocks tumbled down from hillsides.
The aftershock comes after Sunday's devastating 6.9-magnitude earthquake, which relief agencies said wiped out entire villages in the worst-hit regions of northern and western Lombok.
The National Disaster Mitigation Agency placed Sunday's death toll at 82 - many victims were killed by falling rubble while hundreds other were injured and thousands of houses were damaged.
The Pacific Tsunami Warning Center says there was no tsunami threat and there were no immediate reports of damage.
The quake had struck at a depth of 10 kilometres some 195 kilometres west of the town of Mount Hagen.
The Banda Sea quake, which had struck at a depth of 171.5 kilometres, was felt in Australia's northern city of Darwin.