Maritime officials say a cargo ship grounded off New Zealand since October split apart Sunday, spilling cargo containers and debris and sparking fears of a fresh oil spill.

The wreck of the Greek-owned Rena was described as New Zealand's worst maritime environmental disaster, even before pounding waves during a storm tore off the rear section of the ship.

More than 1,000 tons of oil has been pumped off, but more remains on board.

Maritime officials say disaster and wildlife teams have been mobilized and are preparing for any oil that might wash up on the beaches of Tauranga Harbor on North Island.

The captain and navigation officer of the Rena – both Philippine nationals – have been arrested and face multiple charges, including operating a vessel in a manner causing unnecessary danger or risk, and discharge of a harmful substance.