BEIJING -- No new leak point in seabed have been detected at ConocoPhillips' oil platforms in North China's Bohai Bay, with a decrease of the oil sheen on the sea surface, the State Oceanic Administration (SOA) said Sunday.

After on-the-spot check-up at the Penglai 19-3 oilfield, inspection panel from the SOA said that certain achievements have been made in sealing off the oil spills sources, and the oil sheen on the sea surface have been cleaned immediately.

The panel said that the oil leak sources have basically been determined, as well as the possible reason for the sporadic oil sheen.

The spills are now under control, yet one or two liters of oil leak into the sea on a daily basis, and sporadic oil spots on the sea surface are still visible.

The panel stressed that ConocoPhilips 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), ConocoPhilips' 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.