Chinese oil giant CNOOC has said the country's worst-ever offshore oil leak has been sealed, four months after it was first discovered, the state Xinhua news agency reported.
Beijing said the spill at China's largest offshore oilfield, which is operated by US oil giant ConocoPhillips, polluted more than 5,500 square kilometers (2,200 square miles) of sea.
Last month, the government ordered ConocoPhillips to shut down production at the field in Bohai Bay, off China's east coast, announced a thorough investigation into the spill and vowed to punish those responsible.
State-controlled CNOOC, which co-owns the field with ConocoPhillips, said all the leaks have now been been identified and sealed, Xinhua reported late Monday on its Chinese-language service.
"We believe we have met the requirements set by the SOA (State Oceanic Administration) to thoroughly examine and block the oil sources and continue to clean up the oily mud," Chen Bi, CNOOC executive vice-president, told Xinhua.
The government agency, which supervises and manages China's seas, has said it will sue ConocoPhillips over the leak, which was first discovered in June but only made public nearly a month later.
Environmental groups and fishermen accused both companies of covering up the leak of more than 3,000 barrels of oil and oil-based mud -- a substance used as a lubricant in drilling. Both companies denied the allegation.
The incident was China's biggest offshore spill but small compared with the millions of barrels of crude released into the Gulf of Mexico in 2010 after an explosion on a rig operated by British oil giant BP.
ConocoPhillips China, 49 percent owner of the field, said on its website it was "actively accepting the supervision of CNOOC" and "taking additional measures to monitor the seafloor for activity of previously identified or possible additional seep sources."
Last week, CNOOC said it had suspended production at another Bohai Bay platform after a ruptured pipe leaked crude into the water.