A ship cleans up the leaking oil near the platform C in the Bohai Sea, China. [CFP]

China's marine authority said Sunday that certain achievements have been made in sealing off the oil spills sources at ConocoPhillips' oil platforms in North China's Bohai Bay, and no more?leak point have been detected in the area.

The inspection panel of the State Oceanic Administration (SOA) said the oil leak sources have basically been determined, as well as the possible reason for the sporadic oil sheen.?

The panel said that the spills are now under control, yet one or two liters of oil leak into the sea on a daily basis from Platform C of Penglai 19-3 oilfield, and sporadic oil spots on the sea surface are still visible.

The panel stressed that ConocoPhillips should firmly continue the clean-up work in a bid to achieve the complete seal-off of leak sources before winter comes, with the safety as the precondition.

The SOA urged China National Offshore Oil Corporation (CNOOC), ConocoPhillips' partner, to coordinate in the work, calling for immediate release of related information.

More than 5,500 square km of water in Bohai Sea was polluted since June, as oil spilled at the platform, causing the country's worst offshore maritime pollution.

The field is being mined by ConocoPhillips China, the US giant's subsidiary, under a joint development agreement with CNOOC, China's largest offshore oil producer.?