BEIJING - China's Food and Drug Administration has ordered local governments to track the whereabouts of poorly refrigerated and probably ineffective vaccines after police detained a woman thought to have sold nearly $100 million worth of the suspect products nationwide.

The scandal has reawakened longstanding concerns among the public over the safety of food and medicine. Nine pharmaceutical wholesalers believed to have sold the vaccines are being investigated.

The administration on Monday ordered a thorough check on where the vaccines were distributed and how they may have been used. The central government administration demanded local authorities investigate the nine wholesalers believed to have sold the vaccines.

The vaccines included those for hepatitis B, rabies, mumps and Japanese encephalitis. Poorly stored vaccines may lose their potency and cause side effects.

A 47-year-old former doctor has been detained in the eastern province of Shandong for allegedly selling the vaccines to nationwide distributors. Police told state media that the suspect, identified by her last name Pang, had earlier been convicted of illegally selling vaccines in 2009 and sentenced to three years in prison. She was released after the sentence was suspended for five years.

State media reports say Pang sold about 2 million doses of suspect vaccines. Shandong's provincial food and drug safety administration has publicized a list of buyers and sellers.

Amid widespread counterfeiting and lax enforcement, China has struggled to ensure food and drug safety. Past scandals have involved phoney infant formula discovered to be nothing but starch and bogus vaccines containing only saline solution.