Cleanup operations on New Zealand beaches in response to oil leaking from a stranded cargo vessel could go on for some time, an on-scene official said. Cargo vessel Rena is listing badly off the New Zealand coast after striking a reef last week. The cargo ship suffered \"substantial structural failure\" and has a large crack in its starboard side. Maritime New Zealand, the agency overseeing the wreck response, said there were about 500 people on the shoreline around the Bay of Plenty cleaning up oil that has reached the beach. \"This will go on for some time and the same beaches will get re-oiled and re-cleaned on a daily basis,\" said MNZ on-scene commander Nick Quinn. \"This is where it gets exasperating but we have experience in this and will just continue working through the process.\" Quinn said almost 100 tons of solid waste was removed from beaches. He said responders weren\'t using heavy equipment on the beaches because it could make the situation worse. He added that skimmer barges were deployed but the aerial application of chemical dispersants was abandoned because they weren\'t working. Salvage crews boarded the vessel to examine its integrity and operational capacity. There were 88 containers that fell off Rena and 20 have reached the shore. Quinn said there wasn\'t a significant health risk from the contents. Slightly more than 2,500 barrels of oil have spilled from Rena.