At least 37 people have been arrested in China for illegal sales of vaccines, raising questions of product safety.
Three pharmaceutical companies that might have been involved in sales of expired or improperly stored vaccines going back at least four years are being investigated, reports the Guardian.
The case of illegal sales of vaccines was revealed last month when Shandong Province authorities acknowledged the arrest of a mother and daughter in 2015 who were accused of illegally selling vaccines across 20 provinces since 2011 worth $88million.
Following the public outrage, top Chinese leaders also got into the matter.
Chinese Premier Li Keqiang said that there would be "no leniency" for those involved.
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The Supreme People's Procuratorate of China yesterday said that it would directly oversee the investigation.
Beijing has a history of product safety and public health scares.
In 2008, at least six children were killed and thousands fell ill after consuming a toxic chemical called melamine which was found in children's milk powder.