A British charity worker who has recently visited camps holding more than 250,000 refugees in Sri Lanka says there are concerns about the monsoon.
The worker said that military authorities in charge of the camps were treating the forthcoming rains with some urgency.
Last month sudden storms flooded many of the vast camps, submerging toilets and contaminating water.
Thousands of makeshift homes were also damaged in the rainfall.
The monsoon is due next month.
An official of the UK-based Catholic Fund for Overseas Development, or Cafod, Geoff O'Donoghue, visited the camps with two British bishops, and said one of the military officers in charge there was overseeing an extension of the camp to ease crowding.
"As the monsoon comes in there is deep concern, both expressed by the brigadier in the camp and workers in the camp," Mr O'Donoghue said.
"A potential crisis could brew there if the rains come through and those camps are still as congested as they are [now]."
The Sri Lankan authorities are still preventing nearly all those in the camps from leaving.
The government has just announced though that relatives or friends of those inside can now apply to accommodate them.
Such relatives, like the camp dwellers, will also be subject to screening for possible links with the defeated Tamil Tiger rebels.
Meanwhile, the Catholic church has proposed that 12,000 of the displaced people be allowed to move to a large local church and shrine as a first step to returning home.
Mr O'Donoghue said the plan had passed several stages of government approval.