An official checks fake masks at a warehouse in Jing'an District today.

The warehouse is sealed off.

City authorities busted a warehouse where 550,000 fake N95 facial masks were stored and an investigation is underway, Shanghai's market watchdog said today.

Law enforcement officials from the Shanghai Administration for Market Regulation and police raided the Jing'an District warehouse on Monday where almost 1,400 boxes of counterfeit masks were discovered.

They bear the brand "Dasheng" but weren't made by Shanghai Dasheng Sanitation Products, and have a product value of more than 5 million yuan (US$773,239).

"Both the packages and contents were fake," said Shi Li, an inspector with the law enforcement team.

Fake Dasheng masks

Officials launched a citywide campaign against irregularities involving preventive COVID-19 items today.

Dasheng officials said the non-woven fabrics in the fake masks are thinner than the materials the company uses.

Shanghai's market regulators are conducting an intensive campaign against irregularities involving COVID-19 preventive items.

The inspections targeted items such as masks, protective clothing, respiratory machines, thermometers and COVID-19 test kits.

Price gouging, trademark infringement and fake promotions are an emphasis of the inspections.

More than 1,000 companies that manufacture COVID-19 prevention items have been inspected over the past two weeks.