Cyclone Gita was earlier upgraded to a category five - the highest possible.
The office's director, Anare Leweniqila, said damage assessments were on-going, but so far there were no reports of casualties or injuries on Ono-i-Lau.
"We have only received reports of three completely destroyed houses and we are just working around trying to ascertain the nature of these structures."
Mr Leweniqila said it was unclear if the homes were Fijian bures, made of corrugated iron or wood.
Maritime Police were currently travelling from Lakeba by boat to check on the residents of Vatoa Island as there has been no communication with them yet since the cyclone passed, he said.
There will be aerial reconnaissance over the southern Lau group of islands to further assess damage later today.
The government would be mobilised soon to offer support for those affected, Mr Leweniqila said.
Cyclone Gita is moving into waters to the south of Vanuatu and to the north of New Caledonia.
Fiji Met Service said the cyclone had sustained winds of 203km/h at its centre, with gusts of up to 285km/h.
"The cyclone is currently located about 220km south of Kadavu - that's the island within the southern parts of Fiji.
"The cyclone has actually intensified into a category five system as of this morning and it is gradually moving westwards at a speed of 15km/h an hour," forecaster Rajneel Prasad said.