The cargo ship that went missing during a typhoon with 40 people including two Kiwis and almost 6000 cattle on board was hit by a wave and capsized, according to a crewman rescued later.
The Japanese coast guard has rescued one person, a Filipino crew member, who was found drifting in rough waters in a life jacket.
He told the rescuers that the ship's engine failed before it was hit by the wave, and then capsized.
The Gulf Livestock 1 sent a distress signal from the East China Sea after being caught up in typhoon Maysak.
The search for the rest of the crew and ship continues with planes and patrol ships, amid high waves and strong winds from the storm.
The crew of the freighter includes 39 seamen from the Philippines, two from New Zealand, and two from Australia.
According to the Australian government, the man rescued by the Japanese coast guard is one of the Filipino crew.
The Gulf Livestock 1 left New Zealand on 14 August headed for China, with the journey expected to take 17 days.
On Wednesday night, the ship sent a distress call from waters to the west of Amami Oshima island in southwestern Japan.
Strong winds and torrential rains from the typhoon battering the region are hampering the search effort for the ship.
Australia and New Zealand said they were providing consular assistance to the families of their crew members.
Deputy Prime Minister Winston Peters said the Ministry of Foreign Affairs was providing consular assistance to families of New Zealanders involved, and its thoughts are with them.
He said not much was known at this stage, but it was a sad situation for the families.
Because of the maritime traffic in the area, searching would be like looking for a needle in a haystack if there was no emergency signal coming from the ship, he said.
The Gulf Livestock 1 is a 139m, Panamanian-flagged cargo vessel built in 2002.
- BBC / RNZ