The numbers of those buried around Yambali village in Enga province in the country's north are based on estimates from local authorities which have been rising steadily since Friday's landslide.
A UN agency put the estimated death toll at more than 670 people on Sunday.
The National Disaster Centre raised the toll again to 2000 in a letter to the UN on Sunday that was released publicly on Monday.
The landslide also caused major destruction to buildings and food gardens, it said.
"The situation remains unstable as the landslip continues to shift slowly, posing ongoing danger to both the rescue teams and survivors alike," according to the letter.
Villagers carry a coffin for a landslide victim during a funeral procession in Yambali village. (AP PHOTO)
About 4000 people were living near the affected area, CARE International PNG country director Justine McMahon told ABC television on Monday.
But it is difficult to get an accurate estimate of the local population as PNG's last credible census was in 2000 and many people live in remote mountainous villages.
The unstable terrain, remote location and nearby tribal warfare are hampering relief efforts in Papua New Guinea.
Emergency crews, led by Papua New Guinea's defence personnel, were on the ground, but the first excavator only reached the site late on Sunday, according to a UN official.
Social media footage posted by villagers and local media teams showed people scaling rocks, digging with shovels, sticks and their bare hands to find survivors.
Women could be heard weeping in the background.
Six bodies have been retrieved so far. The UN said the number of possible deaths could change as rescue efforts were expected to continue for days.
PNG media on Monday reported that residents had rescued a couple trapped under rubble after hearing their cries for help.
Johnson and Jacklyn Yandam told local NBC News that they were very grateful and described their rescue as a miracle.
The first excavator only reached the landslide site late on Sunday, the UN says. (AP PHOTO)
"We thank God for saving our lives at that moment. We were certain that we were going to die but the big rocks didn't crush us," Jacklyn said.
"It's really hard to explain as we got trapped for nearly eight hours, then got rescued. We believe we were saved for a purpose."
About 1250 people have been displaced by the landslide, which occurred in PNG's Enga province early on Friday.
More than 150 houses were buried and about 250 houses abandoned.
Water continued to flow under the debris, the UN migration agency said, making it extremely dangerous for residents and the rescue team to clear debris.
Serhan Aktoprak, the chief of the UN migration agency's mission in PNG, told ABC television that emergency crews would continue to look for survivors until the residents asked them to stop.
Tribal violence in the region has raised security concerns for road travel, with the military escorting convoys of rescue teams.
Eight people were killed, and five shops and 30 houses burnt down on Saturday, the UN agency said.
