Areas of the sea off North China`s Hebei province where massive numbers of scallops have died are polluted with oil, authorities said.

The latest tests from the North China Sea Branch of the State Oceanic Administration showed oil samples in water near Hebei`s Tangshan city on July 27, and on a beach in Laoting county on July 28, were fuel oil.

An unnamed official from the Maritime Safety Administration told China Daily they also collected oil samples in Laoting, and tests showed crude oil and fuel oil were both detected in nearby seawater.

No huge ship accident has occurred near Hebei province recently, he added.

Instead, suspicions have been directed at an oil spill in North China`s Bohai Bay at a ConocoPhillips China oilfield.

The leak, which started on June 4 and has yet to be stopped, polluted 3,240 square kilometers of seawater at its peak.

However, ConocoPhillips has disputed test results showing it is the company`s oil that is damaging the sea and shoreline.

Since late June, about 70 percent of the scallop seedlings in Laoting have died for unknown reasons, with direct economic losses reaching at least 200 million yuan ($31 million), according to the Laoting Fisheries Association.

Yang Jizhen, chairman of the association, told China Daily on Wednesday that every year about 3 to 5 percent of scallop seedlings die for natural reasons, but it is the first time they have died in such large numbers.

"The oil leak is to blame for the massive deaths," Yang said, adding that it was "too late" to take oil samples in Laoting.

According to a marine environment report in 2010 released by the State Oceanic Administration, increasing oil leaks, such as the Dalian oil spill in 2010, are causing great damage to China`s marine environment.

Qiu Shengyao, a marine professor at Yantai University in Shandong province, told China Daily that oil spills are having a "long-term and terrible" impact on the marine environment.

Of the 17 major rivers monitored across China, about five rivers, including the longest - the Yangtze River - were suffering from oil pollution in the first half of this year, according to the State Oceanic Administration.

China Daily