The 47,230 ton Liberian-flagged Rena hit the reef, about 12 nautical miles (22 km) from Tauranga on the east coast of the country's North Island, early in the morning.
Maritime New Zealand said there were no injuries among the 236-metre vessel's 25 crew, and the vessel was in no immediate danger.
"Weather conditions are very, very good, the current situation of the vessel is stable, there is no oil spill," Maritime NZ spokesman Renny van der Velde told a briefing.
However, the ship has been holed in several places and has a 10 degree list.
"There is significant flooding in two cargo holds, there is a significant amount of water, some pumping has occurred and is ongoing," van der Velde said.
Heavy fuel oil has been pumped from the tanks in the damaged side of the ship. A small amount of hydraulic oil has been detected around the vessel, but was posing no hazard.
A specialist oil spill team was in the area and ready to respond to any escape of fuel oil.
Refloating the vessel was the responsibility of the owners and salvage experts, but any plan would need official approval.
"The vessel is hard and dry on the reef so it may take some time, certainly from current indications this will be an ongoing and quite a long process," van der Velde said, adding it was not yet known how the ship came to hit the reef.
The Rena, operated by the Mediterranean Shipping Co., was headed for the Port of Tauranga , the country's biggest export port, to load further cargo.
The Port of Tauranga, 200 km (120 miles) southeast of New Zealand's biggest city, Auckland, is the country's biggest export port and a hub for transshipping cargo. The district is a popular holiday resort, with long beaches renowned for surfing. (Reuters)
