China's largest oil company, China National Petroleum Corp (CNPC), sought to contain ocean pollution and other impacts from an explosion of two crude oil pipelines in the northeastern port of Dalian, state media reported on Sunday.
Hundreds of firefighters battled for more than 15 hours to extinguish the blaze that started late on Friday when a pipe transporting crude oil from a ship to a storage tank blew up, causing a second pipeline nearby to explode.
There were no casualties, but state television CCTV reported that oil had contaminated a 50 sq km area of the ocean off the port city in Liaoning Province.
Xinhua, citing company officials, said a valve had been closed and oil had stopped leaking into the sea, adding that the spill area had been "fenced off and contained".
But it was not immediately clear how much oil had leaked into the sea.
Calls to the company on Sunday went unanswered.
CNPC, the parent of PetroChina, said that monitoring of the air and sea environment had been stepped up in the affected areas.
The incident drew the attention of top Chinese officials, including President Hu Jintao, Premier Wen Jiabao and security chief Zhou Yongkang, who all issued statements and instructions during the blaze.
The cause of the blast was under investigation.