People walk past a McDonald's fast-food restaurant in Beijing. [Photo Provided to China Daily]

BEIJING - A Beijing company that supplies fries to McDonald's has been fined a record 3.9 million yuan ($655,000) for water pollution, the city's environmental watchdog said on Wednesday.

The penalty imposed on Beijing Simplot Food Processing Co Ltd, a joint venture between US agribusiness giant JR Simplot Company, McDonald's and Beijing Agricultural, Industrial and Commerce General Company, is the largest fine ever meted out by Beijing for pollution.

In November, official inspectors found the chemical oxygen demand in waste water discharged by the company reached 563 mg per liter, exceeding the allowed limit of 500 mg per liter.

Law enforcement officials immediately blocked the company's sewage pipes and ordered it to transport its waste water to a processing plant.

The pollution occurred as Beijing Simplot was upgrading its sewage treatment facilities. The polluted water flowed into urban pipe networks, according to the Fengtai District Environmental Protection Bureau.

The bureau decided on the fine after a hearing in March.

Beijing Simplot, established in 1992 in Beijing's Fengtai district, primarily produces french fries and hash browns for McDonald's and other East Asian customers.

China has strengthened law enforcement for polluters in its environmental protection drive in recent years.