WELLINGTON (Reuters) - United States and Australian aircraft joined the search for passengers of a missing ferry off Kiribati on Tuesday, as rescuers scoured the central Pacific Ocean for a liferaft believed to be carrying survivors.

A handout photo supplied by the New Zealand Defence Force shows survivors from a ferry that sunk floating in a boat in the sea near the South Pacific nation of Kiribati, January 27, 2018. New Zealand Defence Force/Handout via REUTERS

Eight people rescued from an drifting dinghy on the weekend said the ferry broke up soon after setting out on Jan. 18 and that they had seen other passengers scramble aboard a liferaft.

“There is a definitely a possibility that the people in the liferaft are alive given that only a short while ago we found people in an open dinghy alive,” said New Zealand-based rescue coordinator Paul Craven.

“We’re hoping in a liferaft they’re actually in a better survival situation so that’s why we’ve got such an intensive search going today,” he said.

Authorities are uncertain how many people had been on board the ferry, Craven told Radio New Zealand. Reports from survivors and government officials varied between 35 and 100 people.

The 17-metre (56-foot) catamaran was reported missing on Jan. 20, two days after it departed Nonouti Island on a 250 km (155 miles) trip to Betio in Kiribati.

Australia has sent a P-3 Orion surveillance aircraft to assist in the search and the U.S. Coastguard has sent a Hercules aircraft from Hawaii to scour the northern part of the search area.

A New Zealand aircraft spotted a dinghy on Sunday with eight people, including a 14-year-old girl, who had been adrift for days without water. The eight were rescued by a fishing vessel.

They told rescuers they had scrambled into their tiny dinghy as the ferry disintegrated soon after setting off and that other passengers had made it into another dinghy and a liferaft.

The second dinghy had broken up and likely sunk, Craven said, with the search was now focusing on finding the liferaft.

He said rescuers’ main concern was that any survivors would be facing the heat for days without drinking water.