Six Burger King restaurants in Nanchang, Jiangxi province, had operations suspended and were placed under probe for suspected safety violations such as using expired food materials, the city's market regulator said on Friday.

Following a report by China Central Television on Thursday night that accused the restaurants in Nanchang of illegal activities including using expired bread and chicken, the fast food chain has apologized, saying it will cooperate with the investigation and handle the case seriously.

Nanchang's market regulation administration has organized site inspections of the restaurants, focusing on food materials, labels and food processing and storage conditions.

By Thursday night, the administration had seized 85 kilograms of problematic food, it said, adding further investigation is underway.

The administration will conduct inspections on other Western-style fast food restaurants in the city to eliminate safety risks, it said.

In Shanghai, the municipal market regulation administration also launched a probe into Burger King restaurants on Thursday night covering all outlets in the city with a focus on records of food purchases and expiry dates.

The inspection on Thursday night did not find any illegal practices. The authorities required all the outlets to strictly follow related laws and regulations to dump expired food materials.

Following another problem exposed in the CCTV report, the administration also required local e-commerce platforms to see if there are any substandard towels made with recycled materials including used socks or underwear. Towels failing to meet quality standards should be pulled off the platforms immediately, it said.