US fast-food chain Subway is investigating media reports in China that workers at an outlet in Beijing doctored food labels and used produce beyond its expiry date, a Shanghai- based spokeswoman for the firm said.

Reports said workers at a Beijing outlet for Subway, which operates globally as a franchise business, changed expiry and production dates on meat, drink and vegetable produce to extend their use.

“Our headquarters here is now investigating the matter,” the spokeswoman said. She said the firm had not reached any conclusions.

“We want to investigate what caused the labelling issue and whether or not it was the action of a single franchised outlet,” she added.

The issue highlights the difficulty firms have in controlling food quality and safety in supply chains and outlets in China, which can cause serious problems with regulators and hit sales.

Earlier this year, a China-based food supplier to McDonald'sand Yum Brands was caught up in a scandal over workers allegedly tampering with expiry dates, which pummelled China sales at the fast-food chains.

The Subway spokeswoman said the firm sent teams to inspect its franchises around the country each month and gave staff training on food safety and handling produce.

The Beijing food regulator had also launched an investigation, she added.

Subway, part of Doctor’s Associate Inc, has to close 500 outlets in China, according to its official website.

Food safety scandals in China are all too common and include recycled “gutter oil” for cooking, donkey meat products tainted with fox and one in 2008 that involved tainted dairy products that led to the deaths of at least six infants. – Reuters