Yamamoto Chemical Industry Co., a major Japanese manufacturer of pharmaceutical chemicals, has shipped acetaminophen to drugmakers after mixing in Chinese-made stocks of the same chemical without the proper paperwork, health ministry officials said Thursday.

A chemical analysis of the distributed by Wakayama Prefecture-based Yamamoto Chemical found no problems with its quality, and no health damage has been reported, the officials said. Acetaminophen is commonly used in cold medicines and also known as paracetamol.

The Ministry of Health, Labor and Welfare conducted an on-site inspection of the company in May together with the prefectural government, on suspicion it had violated the law on securing the quality, efficacy and safety of pharmaceuticals and medical devices.