SHARES of CNOOC, the country's largest offshore oil producer, slipped 0.74 percent during the morning sessions in Hong Kong Tuesday in the wake of a gas leak report in the South China Sea.

The shares rose as much as 1 percent in first hour before moving into the negative territory to close at 13.48 Hong Kong dollars in the morning trading.

The China National Offshore Oil Corporation said late Monday a gas leak was found in a sub-sea gas pipeline of its Zhuhai Hengqin gas processing terminal.

The oil giant said it shut down relevant platforms in the Panyu 30-1 gas field and the Huizhou 21-1 oil field near the southern province of Guangdong.

No injuries or environmental pollution are reported, and the situation is under control, the CNOOC said.

The platform shutdown will reduce the company's net production by 160 cubic feet per day, and a probe into the cause is under way, it said.

This was the third time this year for CNOOC to report a leaking accident.

Oil spills occurred in the company's Penglai 19-3 oil field, a joint venture with ConocoPhillips China (COPC), in the summer and the Jinzhou 9-3 West oil field in October.