The owners of a Liberian- flagged cargo ship grounded and leaking oil off the east of New Zealand's North Island Thursday apologized to people affected by the disaster, but refused to accept liability.

About 350 tons of oil has spilled and 88 cargo containers have fallen from the 47,000-tone Rena, which ran aground on the Astrolabe Reef, about 12 nautical miles offshore near the port of Tauranga, on Oct. 5.

About 500 dead birds had been recovered and more than 80 oiled birds and at least four seals were in cleaning stations Thursday, according to Maritime New Zealand (MNZ), the country's shipping authority.

Managing director of Greece-based Costamare Shipping Company Diamantis Manos said in a statement that the Rena was in a good condition and the master of the ship had an exemplary record.

The company was working closely with MNZ and other authorities to explain the ship's systems to aid any salvage attempt and would take part in any investigation, said Manos.

"We apologize without hesitation for what has happened," he said.

"It would be inappropriate for us to publicly speculate on the cause of the groundings at this stage. We sincerely apologize to the people of Tauranga and New Zealand for this incident," he added.

Costamare Shipping would also conduct investigations, but any liability would have to be decided under international maritime laws.

The New Zealand general manager of the Mediterranean Shipping Company, which chartered the Rena, said his firm accepted no liability.

Phil Abraham said his company, which had 18 ships under charter with the Greek owners, had been working with Costamare for 20 years with no problems. At present it has 18 ships under charter with the Greek owners.

He told Radio New Zealand that while his company had been involved in the investigation, the grounding was an incident Costamare needed to address with authorities.

"We've entered into a charter with Costamare and they are responsible for the crew and the captain," said Abraham.

"In relation to the incident and the vessel hitting the reef, that's a matter for the owner. That's not our responsibility."

EXASPERATING WORK

MNZ national on-scene commander Nick Quinn said the response from the public to the unfolding crisis had been tremendous, but the clean-up would be a long process.

"This will go on for some time, and the same beaches will get re-oiled and re-cleaned on a daily basis. This is where it gets exasperating, but we have experience in this and will just continue working through the process."

There had been offers to the oil spill response team of heavy equipment to assist the clean-up operation, but, said Quinn, experience had proven this could push oil into the sand and cause further damage to the environment.

"We are considering all oil spill response options, but right now the basic shovel is top of the list, in terms of removing oil from the beach."

Five hundred people were on the beaches Thursday, cleaning up the oil and assessing the potential impacts on shorelines around the Bay of Plenty region.

"Cleaning up the oil remains our priority but we are now dealing with three types of pollutionthe containers, the contents of the containers, and the oil. We have restricted beach access to allow this operation to be undertaken effectively."

A total of 95.45 tons of solid waste and 6 tons of liquid waste had been taken to the waste transfer station Thursday.

Quinn said the Corexit 9500 dispersant being trialled earlier in the week had been shown to be too ineffective to justify aerial application and the aerial application trials had been suspended.

Two skimmer barges were working in the harbor to pick up flotsam and another two would be in operation Friday to collect oil.

A salvage inspection team was winched aboard the Rena early Thursday to check the damage to the vessel and assess whether its power systems were still intact.

The team had assessed whether the vessel Was safe to operate from.

The hoses used to transfer the oil from ship to ship were reportedly largely undamaged and the pumps had no major damage. However, the vessels auxiliary power system was probably not operable.

DANGEROUS GOODS

The vessel was now on a list of about 22 degrees to starboard, and the aft was floating free at high tide while the bow was pinned on the reef. There is a large spilt in the port and starboard hull.

Twenty of the fallen containers had been washed ashore and one container of dangerous goods containing Alkylsuphonic liquid ( UN2586), which was water soluble, had been lost from the ship.

It was not considered a significant health risk, but it could cause some localized effects to the seabed.

Quinn said it was "heart-wrenching" to see the state of some of the birds coming into the cleaning center.

"The mortality rates are starting to increase and there are several hundred dead birds yet to be collected by the wildlife teams who are working methodically to deal with the oiled birds coming in," Quinn said.

More than 370 New Zealand Defence Force personnel with ships, aircraft and clean-up teams have been deployed to the area.

Soldiers from army units around the North Island, armed with shovels and rakes, were on beaches working alongside MNZ personnel and civilian volunteers.

"It's a job that needs to done and we're glad we can help," said Private Clayton Mills.

"The strength of the Defence Force is in its planning ability and the body of skilled and disciplined people who are ready to act when required," said a New Zealand Defence Force spokesman.

The opposition Green Party Thursday called on the government to start putting together a financial support plan for businesses in the Bay of Plenty affected by the disaster.

The Bay of Plenty's fishing sector employed 303 people and was worth 24 million NZ dollars (19.07 million U.S. dollars) in 2006, while the area's tourism sector was worth 435 million NZ dollars in 2009, said Green Party co-leader Russell Norman.