The bodies of 34 Indonesian students have been found under a church which was buried by a mudslide after the quake in Palu, say aid workers.
At least 844 people are confirmed to have died in the disaster, but the number is expected to rise as remote areas are reached.
The aid and rescue operation is being slowed by damaged infrastructure and continuing strong aftershocks.
There are fears some survivors may still be trapped under the rubble.
The bodies of the students were found in the Sigi district, just outside Palu, which was struck by a 7.5 magnitude earthquake and a tsunami on Friday.
Aid workers told BBC they were still in the process of retrieving the bodies, and were being hampered by mud.
"The mud conditions in that area are terrible, we have to walk about 1.5 hours to reach [the mudslide area], that makes it very difficult," Ridwan Sobri, a spokesperson for the Indonesian Red Cross told the BBC.
Mr Sobri said the identities and ages of the students could not yet be confirmed.
According to AFP, 86 students had initially been reported missing from a Bible camp in the Jonooge Church Training Centre in Sigi Biromaru. It is unclear if the students whose bodies have been found belong to the same group.
Blocked roads, a damaged airport and broken telecommunications have made it difficult to bring help into the affected area, and impossible to contact more remote regions.
With hospitals damaged, injured people have been treated in the open and at least one military field hospital has been set up.
The military has taken over the airport to fly aid in, and injured people and other evacuees out.
With supplies limited, people have been raiding damaged shops for food, water and medicine.
"We don't have any other choice, we must get food," one man told AFP.
Mass graves are being dug, one of them to hold up to 300 bodies.
'In the thousands'
The 7.5-magnitude quake occurred at a depth of 10km (6.2 miles) just off the central island of Sulawesi at 18:03 (10:03 GMT) on Friday, setting off a tsunami.
The earthquake was powerful but shallow and with more lateral than vertical movement, not typically the kind of tremor that sets off tsunamis.
Vice-President Jusuf Kalla has said the final death toll could be in the thousands while the Red Cross estimates that more than 1.6 million people have been affected.