About 300 people had evacuated but were now returning to their homes, Butler said.
The Red Cross in Tonga is advising the public to be prepared as Cyclone Gita approaches. It was doing a a U-turn and was expected to head west for several days.
While Gita was upgraded to Category 2 as it threatened Niue on Saturday night, a change of direction lifted the threat and there have been no reports of significant damage.
Its track on Monday morning suggested it would pass close to the main Tongan island of Tongatapu.
The NZ MetService said the cyclone strengthened overnight - meaning the winds in the centre of it could reach up to 167km/h. "It just implies it's becoming a very intense storm when you have an eye forming".
A massive clean up is under way across Samoa and American Samoa after they bore the brunt of the cyclone at the weekend. Gita is now bearing down on Tonga as a category 4 storm.
Tropical Cyclone Gita formed on Tuesday over the Wallis and Fortuna Islands in the southwest Pacific, headed east to the Samoan Islands and is now continuing its clockwise motion and aiming directly for Tonga.
Semisi Sika in a statement declaring the State of Emergency said this is due to the destructive force winds and expected sea level rise brought by this cyclone.
He said the storm's centre was forecast to go south of Fiji, though its southern areas would get high winds and heavy rainfall.
Tonga's Meteorological Service has issues a Hurricane Warning for Tongatapu and 'Eua, as well as damaging swell, heavy rain and flash flooding warnings.
Earlier, Kaniva Tonga reported that Tonga's Minister of Police Māteni Tapueluelu said police had forced a hardware supplier to close down yesterday for breaching the country's Sunday laws.
The Category 3 system is expected to track towards southern Tonga and the southern Lau Group. The country has experienced extensive flooding from Cyclone Gita.
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