Sea Shepherd statement said . `` I guess we can call this nonviolent chemical warfare , '' said Capt. Paul Watson of the Sea Shepherd boat , the Steve Irwin . `` We only use organic , nontoxic materials designed to harass and obstruct ... whaling operations . '' Itsunori Onodera , Japan 's senior vice minister for foreign affairs , described the incident at an international seminar for African and Asian delegates to the International Whaling Commission . He said the Sea Shepherd group threw bags of acid , rather than bottles of rancid butter . Onodera told the audience that the crew complained of injuries afterward , but he did n't elaborate . Sea Shepherd 's U.S. office said it did not know of any injuries . Sea Shepherd interferes with Japanese hunts in an attempt to reduce the number of whales taken . In January , two activists from the group were seized when they boarded another Japanese whaling ship . Japan is lobbying a dozen members of the International Whaling Commission in Tokyo to support its much-criticized Antarctic whaling program . The effort comes before all 78 members of the panel this week in London ,
TOKYO , Japan -LRB- CNN -RRB- -- Anti-whaling protesters hurled containers of butyric acid at a Japanese whaling ship in Antarctic waters , injuring four crew members , a Japanese official said Monday . Activists from the Sea Shepherd Conservation Society hurl objects on to the Japanese ship Nisshin Maru . The Sea Shepherd Conservation Society acknowledged the Sunday incident , saying it had lobbed more than two dozen bottles of rotten butter at the Nisshin Maru , `` sending a stench throughout the whale killing ship that will remain for days . '' Butyric acid is found in rotten butter . The Sea Shepherd boat had to move a half-mile away from the whaling ship because `` it stinks too bad to remain any closer , '' activist Todd Emko of New York said in a statement from the group . Watch protesters toss objects at the ship '' The conservation group said it also threw packets of a slippery chemical on to the deck of the ship , making it difficult to cut up whales . The unnamed substance becomes more slippery when mixed with water so it will be difficult to wash off the deck , a