A response team leapt into action this week to battle the oil that is spilling out of a stranded cargo ship in New Zealand's Bay of Plenty and onto the pristine beaches near the port of Tauranga.

Officials say that some 350 tons of oil may have leaked already from the 775-foot Liberia-flagged Rena, which ran aground on the Astrolabe Reef, just off the port of Tauranga, on Wednesday.

The government has said that the oil spill is New Zealand's worst maritime environmental disaster -- with no end in sight.

Residents of the popular beach towns of Mount Maunganui and Papamoa are bracing for an ecological catastrophe. They have been warned to stay away from the shore and not touch the heavy globs of oil, which authorities say are toxic.

Authorities claim the crisis will take weeks or months to tackle, rather than days. With 1,700 tons of oil onboard - and fuel continuing to leak from the vessel - a wildlife response center has been set up to clean the oiled birds.

About 200 people are involved in the salvage operation, while 300 military personnel are on stand-by to clean up beaches.

Unfortunately bad weather has halted work to pump oil off the ship. A tanker that had been pumping oil from the listing ship, had to return to shore because of heavy swells.

On Tuesday evening, the ship was listing 15 degrees to starboard, according to a report from TV3 News.

Environment Minister Nick Smith said the situation was going to get significantly worse in coming days.

This event has come to a stage where it is New Zealand's most significant maritime environmental disaster, he told a news briefing in Tauranga.

The government is determined to throw everything possible at minimizing the environmental harm of what is now clear to be New Zealand's worst environmental disaster in many decades.

Rena's captain, Mauro Arieves Balomaga, had an unblemished record with his firm until the ship ran aground last week. He will appear in Tauranga District Court on Wednesday. Balomaga, 43, was arrested and faces one charge under section 65 of the Maritime Act, though more charges are expected to follow.

Section 65 covers dangerous activity involving ships or maritime products.

The charge carries a maximum penalty of $10,000, or a maximum term of imprisonment of 12 months, according to Maritime New Zealand.

A number of concerns were raised about the seaworthiness of the Rena, however Maritime New Zealand had inspected the ship at Bluff, on the southern tip of the South Island, and deemed it fit for sail.

The owners of the ship, Greece-based Costamare Inc, have not given any explanation for the incident, saying only that they were co-operating fully with local authorities and every effort is being made to control and minimize the environmental consequences of this incident.

Why the vessel carrying 1,700 tons of oil hit the well-known reef in calm waters remains a mystery.