WELLINGTON: Australian and US aircraft will join the search for survivors from a ferry which sank with 50 people aboard in the remote Pacific, rescue officials said Monday.
A New Zealand Air Force Orion plane, which on Sunday found seven survivors drifting in a dinghy, is already combing a search area larger than Italy.
The survivors -- three men, three women and a 14-year-old girl -- had been aboard the MV Butiraoi, which set off from Kiribati on January 18.
Officials in the island nation raised the alarm on Friday after hearing nothing from the vessel since its departure.
An Australian Maritime Safety Authority jet and a US Coast Guard Hercules agreed to join the search on Monday, Rescue Coordination Centre NZ said.
The centre's senior search and rescue officer Greg Johnston said the remote area where the ferry went missing made it a challenging operation.
He said 385,000 square kilometres (150,000 sq miles) had already been searched and the area was constantly expanding as current modelling was used to estimate where survivors could have drifted.
NZDF Air Commodore Darryn Webb said anyone who was still alive would have been adrift for about a week.
"There's a thought that there could be a liferaft with other survivors on it... we remain optimistic that we may find more survivors," he told Radio New Zealand.
He said the seven people found aboard the dinghy were safely picked up by a nearby fishing vessel and a Kiribati patrol boat would transfer them back to land.
Two commercial vessels are also assisting with the search.
The Butiraoi was last heard from on January 18 when it left Nonouti on a 250-kilometre (155-mile) trip to Betio, the largest township of Kiribati's capital city, South Tarawa.
Local authorities said the 17.5-metre wooden catamaran ran aground and underwent repairs to its propeller shaft before it left Nonouti.
New Zealand sent a military aircraft to conduct sweeps of the area after being called in to help late Friday by Fiji authorities who are coordinating the search.
Kiribati, a nation of 33 atolls and reefs with a total population of about 110,000, lies some 3,460 kilometres northeast of Fiji.