Police have confirmed that wreckage, found in Fiordland today, belongs to the crayfishing boat K'Cee, and the two people aboard were Te Anau men Bruce Robert Gordon, the boat's skipper, and Darren James Allen.
The debris was first sighted off Rocky Point on Secretary Island, which separates Thompson and Doubtful Sounds in an area popular with commercial crayfish boats.
Police were notified at 9.30am today that the 30ft aluminium crayboat was reported overdue, with the two men, aged 42 and 37, aboard.
The last radio report from boat was received at 8.15am yesterday.
Bluff fishermen's radio operator Meri Leask sent a radio broadcast to all vessels in the area asking for help.
Southland Harbour Master Kevin O'Sullivan said the weather was fine and sunny this morning but had been quite rough the past couple of days.
"Nothing like this has happened in the area, but it's a pretty rugged location and we've had a spell of bad weather."
Mr O'Sullivan said the vessel had been in good working order and he was surprised to hear something had gone wrong.
Staff at Te Anau police said they met with Bruce Gordon's family today.
Mr Gordon's wife confirmed her husband was captain of the K'Cee but declined to comment further.
The continuing search includes three helicopters, four local vessels and a DOC boat, and an Air Force Orion was scheduled to arrive at the search site tonight, said Southland Area Commander Inspector Lane Todd.
A briefing later would assess the scale of the search through the night.
A commercial fishing vessel would contain about 5000 litres of diesel, and Environment Southland spokeswoman Michele Poole said they were on standby for an oil spill.
"The search and rescue air craft are watching for oil slicks on our behalf."
In March, Bruce Gordon rescued eight people after their 12 metre catamaran sank in poor weather at Seymour Island.
At the time, police said the people on board had been retrieving craypots when the boat's steering failed and the vessel began taking on water.
The skipper radioed for help while all on board prepared to abandon the boat.
Five people managed to get into a lifeboat and the remaining three swam to shore.
Mr Gordon reportedly responded to the call within 15 minutes and picked up all eight.