This FDA Warning Letter issued to a Chinese manufacturer of medicinal products on 07 February, 2018 is based on an inspection which took place in April 2017.
It was discovered during the inspection that the company did not fully test the active pharmaceutical ingredients and excipients used in the production of their OTC products. It was also criticised that identity testing had only been performed on active substances and not on the excipients used. All batches of starting materials must be tested for identity before the release by the quality control unit.
The company's response from 07 May, 2017, was deemed inadequate by the FDA.
Amongst the points the FDA additionally requested were a detailed sampling plan and testing plan for all incoming starting materials.
Please also see the complete FDA Warning Letter to Shanghai Weierya Daily Chemicals.