The Fiji Disaster Management Office says as many as half the buildings in the Lau Group may have been damaged by Cyclone Tomas.
The office says assessments are still underway but there are initial reports of extensive damage.
The office's operations manager Anthony Blake says more than 1,500 houses and about 50 percent of other buildings, including churches and medical facilities, are likely to have been damaged in the island group.
"Therefore shelter is a significant need at the moment. We are also receiving reports of disruption to water supply. However, water is not the issue, its probably storage. Therefore water containers have been brought in, tarpaulins also brought in as an interim measure, especially for damaged buildings. Purification tablets are brought in, in terms of the need possibly to contain waterborne illnesses."
Anthony Blake says two navy patrol boats are departing this evening with an assessment team and Red Cross supplies for the Lau Group.
He says another boat is taking supplies to the northern division.
He says about 9,000 people are still believed to be in evacuation centres, but there have been no further reports of casualties.
Anthony Blake says a New Zealand airforce plane is heading to Labasa to offload supplies and conduct an aerial survey.
The Australian airforce and French airforce are also expected to be arriving to assist this afternoon.