Trauma from last month's big earthquake in Papua New Guinea's Highlands is still too fresh for many communities to return to their villages.
An International Organisation for Migration (IOM) displacement tracking team has been assessing the situation in Hela and Southern Highlands.
The two provinces were the worst hit by the 7.5 magnitude quake and subsequent aftershocks.
The organisations' Chief of Mission in PNG, Lance Bonneau, said about 20,000 people had been displaced , but he said it was difficult to estimate as landslides had cut off remote communities.
"At this point, assessments haven't been made and teams haven't been able to go up and look at the situation in those villages to see what the prospects of a return would be.
"So I think we're still too close to the earthquake on February 26th; the trauma and the fear are still there, that we're not quite at that point where we can look at returning."
Mr Bonneau said the disaster relief response was gradually becoming more effective.
While he said PNG response teams and their international partners had been hard pressed to reach some of the worst-affected parts due to major road blockages and bad weather, the delivery of basic relief supplies has been improving.
"And I think over theme the effectiveness of delivering this support - food, water, shelter - is going to improve but we still have ways to go. Every day is improving the terms of the co-ordination and getting the assistance out to the needed locations. But over 270,000 require humanitarian assistance, so it's a big task."
Mr Bonneau said villagers feared the land wasn't stable enough now for their homes and gardens.
He said the IOM's displacement mapping would help the government co-ordinate its relief.
The IOM said it had already delivered basic shelter and non-food relief items to over 400 displaced families and funding from the UN Office for the Co-ordination of Humanitarian Affairs, the IOM said it was poised to provide shelter, water and sanitation to another 800 of the worst-affected families in the coming days.