New Zealand Prime Minister John Key says he fears a possible break-up of a grounded cargo ship that is leaking fuel oil from its damaged hull.

Mr. Key told reporters Wednesday that stress fractures have been discovered along the hull of the Liberian-flagged cargo ship Rena, and warned that the risk of the ship coming apart can not be ruled out. The leak has already been called New Zealand's worst environmental disaster.

The Rena has been continually battered by strong winds and heavy waves and is leaning precariously on one side, causing dozens of containers to fall from the ship's deck.

The ship hit the reef off New Zealand's North Island on October 5, carrying about 1,700 tons of heavy fuel oil. Hundreds of tons of oil have been gushing from the ship into the Bay of Plenty and onto nearby beaches.

Health officials have ordered residents to stay off the beaches and out of the sea, and not to touch anything with oil on it. Soldiers have been sent to clean the oil-slicked beach at Papamoa.

The captain of the Rena appeared in court Wednesday in New Zealand's port city of Tauranga and was charged with operating a vessel in a way that caused unnecessary risk. If convicted, he faces a maximum penalty of $7,800 or 12 months in prison. He was released on bail.