A subsidiary of China's largest offshore energy producer CNOOC has said it had not caused a massive fish die-off in Daya Bay, some 40 kilometres east of Hong Kong.
Seasonal oceanic currents were likely to blame, and not air and waste water emissions from CNOOC's Huizhou refinery, said an unidentified representative of the Guangdong subsidiary in an interview published  by China News Service on Tuesday.
Hundreds of dead eels have washed ashore on Daya beaches in the last week, causing alarm among nearby residents about what was causing the die-off.
The administration of the Huizhou industrial zone said in a statement  on Friday that the deaths had been caused by low water temperature, low oxygen and high salt levels.
Locals remain sceptical, however. "With this smell coming out of the plant, how can [refinery] emissions be below national standards?" a resident posted on her microblog. Others expressed concern over emissions from the nearby Daya Bay nuclear power plant.
The refinery started processing crude oil from the Bohai Sea in 2009. It is currently undergoing expansion to increase production to 24 million barrels per day, from 12 million barrels.
The statement comes amid increased sensitivity in China over pollution caused by massive energy projects, two months after citizens voiced their opposition against a gas refinery in Sichuan province and a planned gas refinery in Yunnan province.
Last week, more than 2,000 people demonstrated against a proposed uranium processing plant in nearby Jiangmen, which was later scrapped .