Chinese authorities have formally arrested six employees from a unit of US food supplier OSI Group, the parent company over a scandal involving expired meat sold to fast food giants.

Authorities have previously announced the detention by police of six officials of Shanghai Husi Food Co, a subsidiary of OSI which operated a factory shut down by the city in July for mixing out-of-date meat with fresh products. OSI’s clients in China previously included McDonald’s and KFC.

“OSI Group confirms that 6 employees of Shanghai Husi have now been arrested following detention by 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.