An investigation will consider whether the captain of a stricken cargo ship had been drinking when the vessel ran aground off Tauranga, Transport Minister Steven Joyce says.
The Liberian-flagged Rena was carrying about 1700 tonnes of heavy fuel oil and about 70 tonnes of marine diesel when it struck the Astrolabe Reef at top speed on October 5.
The course the ship should be steering is about three miles to the north of astrolabe reef and there are no obstacles in the way.
He said he would have seen the two flashes of a lighthouse and two white flashes every so many seconds to indicate Mortiti Island.
One possible factor - the ship is believed to not have been equipped with an electronic course plotter, which would have alerted the crew if she strayed from her intended route.
"Our understanding is on the bridge they have radar and they got a GPS that gives them their position and traditional paper charts on the chart table [the equipment] has been enough since World War II and it's kept the port safe."
The ship is put on automatic pilot and a watch keeper monitors the position of the ship and maintains its planned trip.
"He's looking out for the radar. He's looking out through the windows to look for anything that would impede a safe passage."
Lees said an alarm would be sounded when the auto pilot could not keep on course anymore.
But, the reef would not show on the radar because it is too low and there would be no proximity alarms to indicate danger.
