( CNN ) -- The captain and second officer of a container ship that ran aground last year resulting in New Zealand 's worst maritime environmental disaster , pleaded guilty Wednesday to a range of charges . At a court in Tauranga in northeastern New Zealand , the two men pleaded guilty to ten of eleven charges brought by Maritime New Zealand , which included operating a vessel in a dangerous manner , discharging harmful substances and perverting the course of justice by altering ship documents . The identities of the men , both Filipinos , have been suppressed . Currently remanded on bail , they will be sentenced on May 25 , according to a statement from Maritime New Zealand . Willfully perverting justice carries the heaviest maximum penalty of the charges , with seven years of imprisonment . The cargo vessel , Rena , hit a reef off Tauranga in clear conditions on October 5 . At least 350 tonnes of fuel oil spewed into the sea , killing thousands of sea birds and contaminating the beaches of Tauranga 's Bay of Plenty . Efforts to clean tainted beaches and salvage the containers and debris from the stricken ship are still underway .
He and second officer plead guilty to charges of operating a vessel in dangerous manner . The men will be sentenced on May 2018 , with the heaviest maximum penalty seven years imprisonment . Massive salvage and clean - up operations along New Zealand coast are still underway .