Farine's factory, which opened at the beginning of March on the outskirts of the city to meet surging demand, also suspended operations.

"We received a tipoff on Monday from a person who provided their real name," said Wu Jun, a market administration supervisor in the city's Minhang district.

"We found the expired flour and sealed the storage unit that same day."

In total, 578 bags of expired flour that had been imported from France were found in Farine's factory, according to the administration. Inspectors said they believed it had been used to make baked goods.

Xin Xiangrong, who described himself as the lead Chinese partner in the chain, denied selling products that were expired or subpar. He told China Daily that all four Farine branches had been closed voluntarily for an internal investigation to take place.

A Weibo user who claims to have worked for the chain for four months took to the social media platform earlier this week to expose a number of alleged infractions. His post was accompanied by footage that he said had been filmed in the bakery's kitchen while he worked there.

Farine was opened in 2012 by French restaurateur Franck Pecol. Aside from the bakery chain, Pecol also runs an ice cream stand, cafe and a bistro in Shanghai.