A senior official of China National Offshore Oil Company is under investigation suspected of having received bribes, China's top prosecutor said on Thursday, the first executive from the offshore oil and gas firm embroiled by Beijing's war on graft. Luo Weizhong, general manager of CNOOC Gas & Power group, a fully owned subsidiary of CNOOC, had also been detained, according to a statement on the website of the Supreme People's Procuratorate.