More than 500 food manufacturing companies in Shanghai have resumed production disrupted by the COVID-19 resurgence as the city's food industry gets gradually back on track, the city's market regulators said on Wednesday.

As of the end of last year, the city had registered 1,385 food manufacturing firms.

They have been ordered to conduct thorough self-examination and clear expired food and ingredients to ensure food safety, the Shanghai Administration for Market Regulation said.