Maritime New Zealand spokesman Steve Rendle said inquiries would centre around piecing together what had happened onboard.
The investigation would include interviews with the remaining crew members. It would also involve an inspection of Platino.
Mr Rendle said investigators would be trying to clarify what happened to the two men, "and any safety lessons to come out of it."
Three people aboard Platino were rescued by a container ship, which spent 14 hours battling through high seas to reach the stricken yacht.
Auckland City police operations manager Inspector Vaughan Graham said the tug and yacht were met at Northport, Marsden Point, yesterday by a small group of family members from some of those on board and police.
"Police are now investigating the circumstances of Nick Saull's death on behalf of the coroner," Mr Graham said.
The yacht has been towed to a Whangarei boat yard for examination by Maritime New Zealand representatives.
Sea Pelican reached Platino about 8.35am last Friday and had since been towing the vessel.
Mr Saull, a boatbuilder, was remembered by friends as a devoted father and husband who loved the ocean.
The yacht had been due to take part in the Auckland to Denarau, Fiji, yacht race but had pulled out before the June 1 start.