Up to 117 people are now believed to have been on board the Princess Ashika when it sunk late on Wednesday night.
Rescue Coordination Centre New Zealand mission coordinator John Dixon said there are still 62 people unaccounted for and two confirmed dead.
“There is still a significant amount of debris in the water, and we will be targeting those areas.
“Clearly survival rates after this length of time are of concern, but we remain hopeful of finding more survivors,” Mr Dixon said.
A survivor said the vessel rolled so quickly in rough seas that women and children sleeping below decks had no chance to escape.
The crewman said the captain of the Princess Ashika had warned of rough seas approaching with less than a minute’s notice, said Daniel Tuita, operations officer for the Tongan Navy.