Five divers are on their way to scour the water for crew members of a fishing vessel that went missing near Canterbury in a storm yesterday.
A boat was located on the seabed last night but three crew from the FV Jubilee, who sent out a distress call during "brutal" weather about 4.30am yesterday, have still not been found.
Canterbury police said five members of the Wellington-based police dive squad would help with the recovery phase of the operation today.
Inspector Craig McKay said a commercial fishing vessel located an "item of interest" near the FV Jubilee's last known position using sonar yesterday.
Two Coastguard crew members, a representative from Canterbury search and rescue and five dive squad members were making their way to the location this morning, he said.
The boat was sitting on the seabed about 40m below the surface - and it would depend on weather and sea conditions if divers would be sent in as the tide drops, he said.
"While the wind has dropped there are still 1.5m southerly swells in the area," Mr McKay said.
"The dive squad will assess the conditions when they reach the site and hope to be able to deploy their radial sonar to verify whether the item of interest is the FV Jubilee and it's orientation to the seabed.
"If the item is consistent with that of the FV Jubilee the additional data will be assessed along with the weather conditions and sea state before putting any divers in the water."
The recovery was an ongoing process, he said.
It was too early to say whether the item of interest was the FV Jubilee but its location was consistent with the boat's last known position.
Police would provide an update later today, a spokeswoman said.
The Transport Accident Investigation Commission has since launched an inquiry into the sinking of the FV Jubilee, in order to prevent a recurrence.
The incident occurred at 5am on Sunday about 12 nautical miles off the coast near Rakaia, the commission said.
A team of two investigators have begun gathering information and working with search authorities and the fishing company on an investigation plan.
The plan includes options for inspecting the sunken vessel.
The commission said the aim was to find out what has happened and why in order to prevent a similar situation happening again.
Search efforts began at 6.30am yesterday with a plane later spotting debris from the Jubilee, Inspector Craig McKay of Canterbury police said.
A boat taking part in the search then recovered an empty life raft, confirmed as belonging to the vessel.
Fishing bins and documents were also found, as was oil and other fluids.
The police conveyed news of the empty life raft's discovery to the men's families, who, they said, were devastated.
By mid-afternoon, police said the rescue phase of the operation had ended and the "recovery" phase had begun.
The Jubilee went missing 12 nautical miles (22km) from the Rakaia River mouth, south of Christchurch.
Andrew Stark, chief executive of the vessel's operater Ocean Fisheries, said conditions at sea were rough, with winds blowing up to 40 knots (74km/h).
The searchers had to battle 3m swells and choppy waters, he said.
It wasn't an easy search from the air or from the sea.
The three men on board were familiar with the Jubilee, Mr Stark said.
"They're all experienced with the boat."
One of the men on board was believed to have family in Motueka.
The air and sea search covered about 170sq km.
The Jubilee's last-known location was in a spot where the waters were up to 45m deep.
Two Coastguard boats, three commercial vessels, a Westpac rescue helicopter and an aeroplane joined the search.
Coastguard Southern Region said the rescue boat Blue Arrow Rescue went to the Rakaia River mouth area "in difficult conditions" to search for survivors.
Coastguard Canterbury also joined the search, heading south from Pigeon Bay near Akaroa.
The Jubilee was launched in January 2008.
At that time, Stark Bros said the boat would fish the "varied conditions and fishing grounds" off the South Island east coast, in seas from 10m to 500m deep.
Additional reporting: Vaimoana Tapaleao and John Weekes