Premier Li Keqiang answers media questions at the news conference after the closing meeting of the fourth session of China's 12th National People's Congress at the Great Hall of the People in Beijing, March 16, 2016. [Photo by Xu Jingxing/chinadaily.com.cn]

Chinese Premier Li Keqiang vowed no leniency for anyone involved in the black market sales of problematic vaccines, after a case was made public involving $88 million worth of illegal vaccines that are suspected of being sold in dozens of provincial-level regions around the country.

Li also pledged to punish officials who are proved to have committed dereliction of duty in the spreading of the fake vaccines.

The police recently discovered that improperly stored or expired vaccines, worth more than 570 million yuan ($88 million ) have been allegedly sold in more than 20 provincial-level regions since 2011.

Police in East China's Shandong province announced last month that they had detained 37 suspects implicated in the vaccine scandal, including a mother and daughter alleged to have illegally sold the improperly stored or expired vaccines, and people from three pharmaceutical companies, according to the work group handling the case.

Meanwhile, the group has ordered a sweeping check-up of local vaccine makers, wholesalers and buyers.

China's drug regulator has identified nine vaccine wholesalers from six provinces suspected of filing fraudulent reports of buyers' identities.

The Supreme People's Procuratorate (SPP) on Tuesday announced it will directly oversee the problematic vaccine case, and urged prosecuting bodies at all levels to spare no efforts in their investigation.

Prosecutors across the country will work closely with local police and drug administrations to uncover the manufacturing source, circulation channels and buyers of the inferior products.

The SPP also ordered a quick response mechanism to be established to facilitate information sharing, case details and case transfers.