By Charles Haviland
BBC News, Colombo
The downpours reportedly washed away tents, toilets and sewage pipes
Heavy rains in northern Sri Lanka continue to cause suffering at the vast government-run camps where internally displaced people are held, reports say.
Heavy and sudden showers since Friday have caused havoc at the main complex of refugee camps at Manik Farm, home to some 230,000 people.
The UN humanitarian affairs office says one zone is totally under water.
In another zone, 95 toilets are submerged, water is contaminated with sewage and soakage pits have collapsed.
The government is limiting access to the camps by aid agencies, journalists and other outsiders.
Photos sent from the camps show what looks like a sea of mud, but the UN says it has no information on the situation in one of the zones, and there are varying accounts of the overall picture.
One newspaper says 100,000 people have been left with no proper shelter, but a news website puts the number of families temporarily relocated at only 1,000.
The UN says that because of the bad weather, the authorities are now trying to speed up the resettlement of the refugees to their home districts.
So far this process has been going slowly, with the government insisting it has to screen all refugees for possible links to the Tamil Tiger (LTTE) rebels.
Defence Secretary Gotabhaya Rajapaksa was quoted on Monday as saying that "LTTE terrorists masquerading as civilians" could resume attacks if released from the camps.
But opposition leader Ranil Wickramasinghe said the conditions in the camps were worsening - and so too was Sri Lanka's reputation as a result.