The BBC reports that Chinese officials have ordered pharmaceutical companies to check their suppliers following claims that some have used "gutter oil" to make antibiotics. Gutter oil is reprocessed kitchen waste dredged from restaurant drains.

Officials are currently investigating whether cheaper "gutter oil" rather than soy bean oil has been used in the production process.

via BBC News - China probes gutter oil in medicine claims.

According to the Wiki entry for gutter oil: Gutter oil is a term used in China to describe illicit cooking oil which has been recycled from waste oil collected from sources such as restaurant fryers, drains, grease traps and slaughterhouse waste. Reprocessing is often very rudimentary; techniques include filtration, boiling, refining and the removal of adulterants. It is packaged and sold as a cheaper alternative to normal cooking oil. Other forms of gutter oil may use discarded animal parts, animal fat and skins, internal organs, and expired or otherwise low-quality meat boiled up in vats to extract residual oils.