( CNN ) -- The captain and second officer of a container ship that ran aground last year , resulting in New Zealand 's worst maritime environmental disaster , have been jailed for seven months . Maritime New Zealand ( MNZ ) said in a statement Friday that skipper Mauro Balomaga and Navigator Leonil Relon -- both Philippines nationals -- were found guilty of a total of 11 offences , including operating a vessel in a manner causing unnecessary danger or risk , discharging harmful substances , and willfully attempting to pervert the course of justice by altering ship 's documents subsequent to the grounding . The cargo vessel , Rena , hit a reef off Tauranga in clear conditions on October 5 last year . At least 350 tons of fuel oil spewed into the sea , killing thousands of sea birds and contaminating the pristine beaches of Tauranga 's Bay of Plenty . After a passage plan for the vessel 's journey had been plotted , the captain gave approval for the second officer to deviate from the plan to save time , MNZ said . The subsequent changes to the ship 's course , which were not verified using appropriate navigational methods , put the vessel directly on target to hit the Astrolabe Reef . About 10 minutes before the grounding , the reef appeared as an echo on Rena 's radar . At this stage , there was still sufficient time to make an effective alteration of course and avoid the reef , the MNZ statement said . The captain saw the echo and assumed it was a small vessel -- but when he could not find it , he dismissed it as a false echo . These two senior officers , who were responsible for the safe navigation of the ship , had failed in their duty , MNZ director Keith Manch said . Click here for latest on the clean-up operation . `` In this case , the master and the second officer have breached the most basic fundamental principles of safe navigation , '' he said . `` If there is a need to deviate from a prepared passage plan , the alterations must be plotted and the new projected path carefully assessed to ensure all potential navigational hazards are identified . '' Manch added that both officers also admitted making alterations after the grounding to the ship 's GPS log , its passage plan and its computer to mislead investigating authorities . `` This offending is also very serious in that it caused genuine confusion for investigators trying to piece together the events that led to the grounding , '' he added . `` It is vital that when these types of events do take place , we can find out how and why they have happened to help prevent such an event happening again . '' Earlier this week , MNZ said `` excellent progress '' has been made on container removal from the wreck site over the past week , with 21 containers removed from the bow section of the vessel on Monday -- the highest number of containers removed in a single day since the break up of the wreck . It said 815 of the 1,368 containers on board have now been recovered . It added that tons of debris , such as timber and plastic continues to be removed from the Bay of Plenty coastline on New Zealand 's North Island .
Captain , second officer given seven months for offenses including operating a vessel in dangerous manner . At least 350 tons of fuel oil to spewed into the sea when cargo ship Rena hot a reef off New Zealand . Massive salvage and clean-up operations along New Zealand coastline are still underway . Comment: