A collision between a Japanese whaling vessel and a high-tech protest boat off Antarctica was the fault of both captains, New Zealand has ruled.
The 6 January collision cut the bow off the protest boat.
But Maritime New Zealand said that there was no evidence either side deliberately caused the collision, instead blaming poor seamanship.
It occurred as protesters from the Sea Shepherd environmental group sought to thwart Japan's annual whale hunt.
Japan abandoned commercial whaling in 1986 after agreeing to a global moratorium.
But it says that whaling is part of its culture and catches hundreds of whales each year as part of what it calls a scientific research programme.
Conservationists say the whaling is a cover for the sale and consumption of whale meat. Every year activists follow the fleet to Antarctic waters and attempt to disrupt it.
Sea Shepherd had accused the Japanese ship, the Shonan Maru 2, of deliberately ramming its boat, the Ady Gil. The Japanese vessel said the protest boat drove into its path on purpose.
The report by Maritime New Zealand said that several incidents in days leading up to the collision had "contributed to a tense operating environment and probable uncertainty over each other's intentions".
Poor seamanship on both vessels then led to the collision, it said.
"(It) appears to have resulted from a failure by both masters and the crew of both vessels to appreciate and react appropriately to the potential for the collision," the inquiry found.
Japanese officials said they needed to study the investigators' report before commenting.
Peter Bethune, captain of the Ady Gil, said the Japanese vessel had "disobeyed all of the rules".
A month after the collision, he boarded the Japanese vessel, saying he wanted to protest about the collision.
He was then taken to Japan where he spent five months in jail before being convicted of several charges and deported to New Zealand.