日韓討論韓艦沉沒事件

Recently the NHK News reported the following:

岡田外務大臣は、訪問先の韓国で、ユ・ミョンファン外交通商相と会談し、北朝鮮の関与が疑われている韓国の哨戒艦の沈没について、今週にも公表される調査結果を踏まえ、日本と韓国、それにアメリカが連携して対応していくことを確認しました。
会談の冒頭、岡田外務大臣は、北朝鮮の関与が疑われている韓国の哨戒艦の沈没について、「きわめて困難な状況のなかで、韓国政府がきぜんと冷静に対応していることに敬意を表したい。日本政府は韓国を支持しており、必要な協力は惜しまない」と述べました。これを受けて、会談では、ユ・ミョンファン外交通商相から現在、韓国がアメリカなどと合同で行っている調査の進ちょく状況などの説明が行われ、両外相は今週にも公表される調査結果を踏まえ、日本と韓国それにアメリカが連携して対応していくことを確認しました。一方、韓国政府が竹島周辺の海域でボーリング調査を行ったことについて、岡田大臣は「注意深く抑制してもらいたい」と述べ、日韓関係に影響を及ぼさないよう慎重な対応を求めました。会談のあと、岡田大臣は「ユ外交通商相からは哨戒艦の沈没について、調査の話が中心だったが、今は詳しいことは申し上げられない。日米韓で連携をとってやっていかなければならない」と述べました。

Foreign Minister Okada at his visiting destination South Korea had talked with Minister Yu who was responsible for diplomacy and trade about the sinking of the South Korea patrol warship, and based on the result of the survey made public this week a join effort of Japan and South Korea and together with the co-operation of the US to respond to the matter was confirmed.

At the beginning of the meeting, Foreign Minister Okada, regarding the sinking of the South Korea patrol warship in which the involvement of North Korea was suspected, had said that "even in such an extremely difficult situation the South Korea government had responded to the incident calmly and this had my respect. Japanese Government would support South Korea, and to give the necessary assistance without reservation". This was accepted, and at the conference, from Yu the Minister for Diplomacy and Trade the progress of the investigation that South Korea was doing jointly with the United States etc. was explained, and the two Foreign Ministers based on the result of the survey made public this week, confirmed Japan and South Korea cooperation together with the United States to work out a response. On the other hand, regarding South Korean government drilling survey in the sea area around Takeshima, Foreign Minister Okada had expressed "hope it would be controlled carefully", and requested a cautious reaction so as not to affect the relation between Japan and South Korea. After the conference, Foreign Minister Okada had expressed that "with Yu the Minister for Diplomacy and Trade, the sinking of the patrol warship and its investigation was the center of discussion, though details could not be said now. It is necessary for Japan-U.S. South Korea to come into co-operation".

The sinking of the South Korean patrol boat had probably drawn South Korea and Japan closer in terms of diplomatic relationship. I am wondering which countries are helping South Korea to do the investigation: Japan, the US and China?