Port Moresby - Papua New Guinea authorities scaled back their search on Sunday for survivors from the sinking of a passenger ferry, saying none of the more than 100 people still missing were likely to be found alive.

The Pacific nation's National Maritime Safety Authority (NMSA) moved from search to recovery mode after scouring the waters for 56 hours without finding a survivor of Thursday's sinking of the MV Rabaul Queen near the city of Lae.

“Whilst rescue operations are likely to continue, weather permitting, for some more time, basically we are looking for bodies from now onwards,” said NMSA rescue coordinator Nurur Rahman.

A fifth body was found on Sunday but Rahman said the number of survivors remained the same at 246 and there was little hope, given the thoroughness of the search and amount of debris picked over, of finding any others.

“There is a high degree of confidence, that if there were any active survivors or persons inside life rafts or with lifejackets within the search area, that they would have been sighted and recovered by now,” he said.

The ferry went down after being hit by what its operator described as a freak wave in the early hours between the popular New Britain dive spot Kimbe and Lae, carrying 351 passengers and 12 crew.

It is believed to be among PNG's worst sea accidents.

Military and police observers flew over the scene in fixed-wing aircraft and the coastline was scoured by helicopter from south of Finschafen to north of Fortification Point without spotting a single survivor.

Strong winds forced the suspension of aerial surveillance on Sunday afternoon and Rahman said it was unlikely to resume unless there was “significant intelligence information”.

PNG disaster officials were meeting with the relatives of victims twice daily at Lae to keep them updated with developments, he added.

Canberra said an Australian military aircraft sent to help with the search returned home overnight after completing its mission.

“The Australian government greatly regrets the loss of life following the sinking of the MV Rabaul Queen and will offer any assistance we can to Papua New Guinea,” said parliamentary defence secretary David Feeney. - Sapa-AFP