SHANGHAI (AFP) - The Chinese authorities have formally arrested six employees from a unit of United States food supplier OSI Group, the parent company and the government said, over a scandal involving expired meat sold to fast-food giants.

The authorities had previously announced the detention by police of six officials of Shanghai Husi Food Co., a subsidiary of OSI that operated a factory shut down by the city in July for mixing out-of-date meat with fresh product. OSI's clients in China previously included McDonald's and KFC.

"OSI Group confirms that six employees of Shanghai Husi have now been arrested following detention by the authorities," the company said in a statement provided to media. "OSI Group will continue to cooperate fully and in good faith with the authorities," it said, but did not identify the six.

Shanghai's prosecutor's office said the employees were suspected of producing and selling "fake and inferior" products, according to a separate statement posted on its website.

The scandal, which came to light after an investigative report by a Shanghai television station, caused shock waves because Western chain restaurants are widely viewed as upholding higher quality standards in a country hit by repeated food safety problems.

The OSI Shanghai factory's customers in China also included Pizza Hut, coffee chain Starbucks, Burger King, 7-Eleven convenience stores and Papa John's Pizza.

McDonald's restaurants in Japan and Hong Kong were also affected.

McDonald's has severed its relationship with OSI in China, but the change in suppliers caused widespread shortages of its menu items in the mainland, including Big Macs and Chicken McNuggets, for more than two weeks.

The Chinese government is now investigating OSI, while the US company is also conducting its own internal probe after shaking up its management in China.