CNOOC, China's largest offshore energy explorer, said Thursday that it would repair a leaking pipeline after inert gas replaces natural gas in the South China Sea, and no oil spill was reported.

The undersea pipeline will be repaired after nitrogen replaces natural gas, said Gao Guangsheng, vice president of CNOOC's Shenzhen branch, which manages the terminal.

The leak was detected Monday by fishermen about 12 kilometers from the natural gas terminal in the city of Zhuhai, Guangdong province, and after four days of active pressure venting, the internal pressure of the pipe is approaching the appropriate level for repair, Gao said.

Injections of nitrogen started Thursday morning as a dredger surveyed the pipe's surroundings for repair work. However, winds were too strong on the sea Thursday, making it a bad time for doing repairs.

Gao said no oil spill was detected, no casualties were reported, and the situation was under control.

The report was echoed by China's State Oceanic Administration, which announced Thursday afternoon that no oil spill had been reported at the scene but sporadic oil was detected.

Marine authorities and police quarantined the sea area.

Ten water sampling stations have been set up, and they reported that the water met quality requirements and burnt embers from the leakage point had been spreading to the outer sea area, according to the report from the South China Sea branch of the State Oceanic Administration.